Planned order in PS& PP Scenario

Dear Expertes

                          we create reservation at operation WBS ( as a Activity).We run project based MRP through MD51.

My Issue is "when the WBS In project & sales order is same then system club requirement of project & sales order if it is different then why sales order not create planned order" ?.

Refer screen shot 1 :  Where WBS in project and sales order is different .

Reservation =300, Sales order =30, Stock =25 . Planned order =300-25 =275Image may be NSFW.
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Refer screen shot 2 : where WBS in project & sales order is same. So system is clubbing requirement

Ex :

         Reservation =300, Sales order =30, Stock =25 . Planned order = 300+30-25=305

Image may be NSFW.
Clik here to view.