Mrp not considering manual reservation from PP order

Hi,

How can MRP will consider manual material reservation (creating by pp-order CO01) into account while MRP run ?

thisi is my scenario:

Mrp type = V1

Lot size = HB with maxium 20000

In OMDQ i've activated all Indicator under the tab add. ext. req. in the reorder point planning and settting External reqmts within replenishment lead time.

Purchase requisition quantity from MRP run: 13000 while i expected 14560

thanks