A reference band is a shaded area that shows a range of values on an axis. You can use a reference band to highlight a target range, a confidence interval, or a standard deviation. In this case, you want to add a reference band that shows the range of values from 0 to 100 on the y-axis. This will create a shaded area behind the bars that indicates the percentage of sales.
To add a reference band, you need to do the following steps:
Click on the Analytics tab on the left side of the workbook to open the Analytics pane. You will see a list of analytical objects that you can drag and drop onto your worksheet.
Drag Reference Band from the Analytics pane to Y-Axis on the worksheet. This will add a reference band on the y-axis that shows the average and confidence interval for all values.
Click on the Edit button on the reference band to open the Edit Reference Band dialog box. You will see options to customize your reference band.
Change the Band From value to 0 and the Band To value to 100. This will change the reference band to show the range of values from 0 to 100 on the y-axis.
Click OK to apply the changes. You will see that the reference band now shows a shaded area behind the bars.

check the steps below in explanation
Explanation:
To filter the table to show the members of the Top10 set and the Bottom10 set, you need to do the following steps:
Open the link to Book1 found on the desktop. This will open the Tableau workbook that contains the Disciplines worksheet.
Click on the Disciplines tab at the bottom of the workbook to open the worksheet. You will see a table that shows the disciplines, sales, and profit for each salesperson.
Click on the drop-down arrow next to Salesperson on the Filters shelf. This will open a menu that allows you to filter by different criteria.
Select Set from the menu. This will show you the sets that are available for the Salesperson field. You will see Top10 and Bottom10 as two sets that have been created based on the sales ranking.
Check the boxes next to Top10 and Bottom10. This will filter the table to show only the members of these two sets. You can also click on All to deselect all other values.
Click OK to apply the filter. You will see that the table now shows 20 rows, 10 for each set.