Hi..
As soon as you input activity quantities using PP’s Confirmations function,
Direct cost center connected to work center have credit’s amount usingbelow Formulas.
Credit amount = actual activity qty * plan price (kp26).
Cost center don’t have a COGS.
You can transfer the variance between actual and standard into c-pa throught settlement after you execute the below period end closing job.
-. cost allocation
-. Revaluation of activities at actual prices
-. Overhead calculation
-. WIP calculation
-. Variance calculation
-. Settlement
You should study the concept for product costing through sap help portal site: