Withdrawal Quantity and MRP Run

Dear All

We run MRP based on the PIR quantity updated in MD61. Now I see that if I run the MRP say on 7th Jan and my PIR is for 1000, in MD62 it considers only 800 for planning and displays 200 as withdrawn qty. But this 200 was withdrawn for last month plan, but it has been done this month. How do we control this so that system considers 1000 as plan.

Secondly I see that for few materials only withdrawn quantity is displayed and for few it is not displayed. What may be the reason for this.