Partially delivered orders which was not issued consuming allocations from QTTAB

Hello Dear Experts,

I came across a strange issue in APO GATP where i see the partially delivered items which was not goods issued yet(Open deliveries) consuming allocations from QTTAB in APO upon back order processing ,which is incorrect according to my opinion.I have checked all the config setting in APO GATP and every thing seems to be perfect.We are configured to consume allocations based on sales order MAD date in QTTAB.

Can you please throw some light on this issue.

Thanks

Mani