PPAC has outstanding GL amount when no onhand balance in inventory

Hi

I use PPAC for cost calculation method.

Date              Transaction Type      QTY      Item Cost/Price            GL Amount
20-Jan-12     Receiving                     10          5                                50
25-Jan-12     Misc Isssue               - 10          5                               -50

Inventory value is (0*5) = 0 and GL amount is 0

03-Feb-12     Receiving                    10          9                                 90
05-Feb-12     Misc Issue                 -10          7                                -70                  ( PPAC Item Cost = (50+90)/(10+10) = 7)
                                                                                                         ------
                                                           0                                              20
                                                                                                         ====

Inventory value is (0*7) = 0 and GL amount is 20

Is my understand correct?

What should I do next to make inventory value equal to GL amount?

Is cost revaluation option when run OPM Accounting Preprocessor help?