Setting up Calculation of Actual Capacity Requirements 
Use
You can use this procedure to specify whether actual capacity requirements are calculated from confirmations of quantities or activities and how they are calculated.
The system calculates actual capacity requirements from:
Procedure
Enter one activity for each actual capacity requirement in Actual capacity requirements from activities. Determine the standard value parameter that identifies the corresponding activity.

You can display the standard value parameter of the resource by choosing the F4 help.