PO with account assignment category Q is fetching wrong GL

Dear Experts,

I am creating a purchase order with account assignment category as "Q". In Account assignment tab it is picking G/L assigned to GBB-VBR (Consumption acc. G/L) . It supposed to pick the stock G/L assigned to BSX as the material is going to project stock. after MIGO the material stock is being updated. Please let me know why the PO is poking consumption G/L in place of stock G/L. In my OBYC setting the BSX and GBB-VBR are maintained against the valuation class of the material.

Thanks

Regards

Chinmaya