Dave,
The last field in the query should have the following expression: QTyOnHandCalc: Nz([SumOfUnitsReceived])-Nz([SumOfUnitsSold])-Nz([SumOfUnitsShrinkage])-Nz([SumOfUnitsUsed])+Nz([SumOfCycleCountCorrection])
Don't use spaces in the name Variable QTyOnHandCalc. The Nz() function will convert any NULL entry to 0 because if you add or subtract a NULL from a number the result will be NULL
I still maintain that Product ID 1 belongs to Mfg Part No. 19800 and has four records (if you apply a filter for Product ID = 1).