Comprehensive and Detailed Explanation From Exact Extract:
The handbook lists several key factors for tailoring RE processes: degree of shared understanding between stakeholders and team, available time and budget, trust, system complexity, criticality and volatility of requirements. High volatility and low shared understanding typically call for more iterative and rigorous RE.
Limited time and budget favour lightweight approaches. The sheer number of requirements may affect workload but is not considered a primary factor in deciding process facets such as linear vs. iterative or customer-specific vs. market-oriented. Thus, "quantity of requirements" is not one of the main influencing factors.