It is possible, if you set up your Quantity Structure Category in Quantity Structure Type as NOT percentage value. SPRO: Controlling/ Product Cost Controlling/ Selected Functions in Material Costing/ Mixed Costing.

OKEQ - click on the proper 'plan/actual' vesion, double click on 'setting of each fiscal year' - define a missing fiscal year if does not exisit. Double click on a defined fiscal year: check and change if necessary settings under 'price calculation' ...