Reference https://docs.oracle.com/cd/E37583_01/doc.1116/e22598/F458900AN13D82.htm How Resource Mapping Is Calculated You can track the cost impact of every resource that has been assigned to a project task and use the resource breakdown structure to view the breakdown of these costs. Oracle Fusion Projects associates the costs of the resources used for tasks with branches and levels in the resource breakdown structure. The process for determining the correct association is managed by rules of precedence.
Oracle Fusion Projects uses the following rules to associate cost amounts with resources:
Select the lowest level in the resource breakdown structure to which a transaction can map.
If there is only one level to which the transaction maps, the cost amounts are mapped to that level.
If the transaction maps to more than one level, Oracle Fusion Projects sums the precedence numbers for all resource types in the branch and gives precedence to the resource element in the branch with the lowest sum.
If more than one branch has the lowest precedence number at the lower level, the application uses the precedence number of the next level up.
If the sum of precedence numbers is the same for more than one branch, precedence is given to the branch with the lowest number at the lowest level.
If one branch contains a user-defined resource type, precedence is given to the branch that does not contain a user-defined resource type.
Note Oracle Fusion Projects gives more precedence to a lower precedence number. For example, a resource element with a precedence number of 1 is given precedence over a resource element with a precedence number of 10.

Ref:https://docs.oracle.com/en/cloud/saas/project-portfolio-management/19a/faopm/subjectareas.html#Projects__Cross_Subject_Area_Analysis__Real_Time_SA_20 Analyze real-time information on project performance, including budgets, forecasts, costs, commitments, revenue, and invoices.
This subject area analysis allows cross subject area analysis between Funding, Invoices, Revenue, Budget, forecasts, Costs areas.

Ref: https://docs.oracle.com/en/cloud/saas/project-portfolio-management/19b/oapfm/project-foundation-configuration-define-project-resource-breakdown-structures.html#OAPFM180158_2 Why can,t I find persons in the list of resources when I enter team members, planning resources, or person rate schedules?
You can,t find persons in the list of resources when you enter team members, planning resources, or person rate schedules in the following situations:
The administrator didn,t assign a department while creating users. Persons must have an active assignment and be assigned to a department in Oracle Fusion Human Capital Management before they can be added as team members or entered as resources on the planning resource breakdown structure or person rate schedule.
The resource isn,t active in Oracle Fusion Human Capital Management because the current date is before the effective date of the resource. If you want to include persons who will start in the future, select the Include people with future-dated effective start dates option when you search for the person.
Persons assigned as project managers aren,t active as of the project start date.
The assignment of the person is terminated, and an appropriate value isn,t set for the number of days to display people with terminated assignments. You can set the profile value appropriately at the site profile level using the Specify Number of Days to Display People with Terminated Assignments task in the Setup and Maintenance work area.

Ref: https://docs.oracle.com/en/cloud/saas/project-portfolio-management/19b/oapjb/create-customer-contract.html#OAPJB70183 Bill Plan - Create a bill plan within a contract that uses the invoice method you require. Assign the bill plan to one or more contract lines. A set of instructions on a contract that define how to invoice a customer. Multiple contract lines on a contract can use the same or different bill plans. Invoice Method is used in creating Bill Plan - not a separate setup.
Billing Controls - Contract feature that controls the types of transactions, dates, and amounts a customer may be invoiced for and revenue can be recognized for a contract or contract line. Define billing controls at the contract or contract line level.
Topic - Creating a Contract for Percent Spent Invoice and Revenue Methods: Worked Example This example describes a scenario where transactions for a contract line need to be invoiced and the revenue recognized using the percent spent method.
What are the revenue and invoice method classifications? Percent Spent What is the billing extension calculation level for the contract line and project association? Project level Summary of the Tasks Create a contract, create the percent spent contract lines, create the bill plan, create the revenue plan.
Prerequisites
Create a project.
Create the project plan for percent spent revenue. Specify the plan type on the percent spent billing extension.
Create an approved cost budget.
Create cost and burden rates.
Enter labor and expense transactions for the project.
Collect costs for the transactions.
Configuration Steps
Creating the Contract
Creating the Percent Spent Contract Lines
Creating the Bill Plan - A set of instructions on a contract that define how to invoice a customer. Multiple contract lines on a contract can use the same or different bill plans.
Creating the Revenue Plan - Common set of instructions for recognizing revenue within a contract. Multiple contract lines on a contract can use the same or different revenue plans.
Invoice method classifications determine how transactions are invoiced. The invoice method determines how invoice amounts are derived.
Enter an invoice method on a bill plan, which you create for a contract and assign to contract lines to provide a set of instructions for creating an invoice.
Create billing controls for a contract or contract line to define the valid transaction dates, billing resources, and amount limits for transactions associated with the contract.
Generate invoices to calculate the invoice amounts for a contract.
The following figure illustrates the components of a project and a contract that determine invoice amounts, and the relationships between the components.