PPDS heuristic is not generating receipt element for particular type of req

For a particular type of sales order the required quantity is not appearing in the REC/REQ quantity column of /SAPAPO/RRP3 screen - element Tab.

But the quantity is appearing in the Requested Quantity - Column.

As a result heuristic is not considering the requirement and not creating the receipt element

Can anybody suggest what is the problem?

Regards

Mridul