Subassembly Overrun Costing Issue

Vantage gurus,

We have a job containing 3 sub-assemblies for outside processing of components.  On each of the sub-assemblies we had an overrun of 6 units which we put to stock.  When the 6 overrun units were put into stock it appears that the system used the Estimated Material cost but the Actual Subcontract cost to calculate the final unit cost.  As the Estimated Material cost is higher than the Actual Material cost the value of the 6 overrun units is vastly overstated.  Has anyone else had this happen and if so what is the fix?

Wendy Hodgson