Debit memo request (DP91) - Parent Sales order: Net Order Quantity, Value differ

A parent sales Order is created with Ex: 10Units. Then a debit-memo request document is created w.r.t the parent sales order (DP91). The “Target quantity” displayed in the debit-memo request is only 1Unit and the Net Value of the order is equal to the Price of 1 material unit. Please share your thoughts of why there is a difference in the “Target Quantity” and what I should do in order to populate the actual quantity.

Note: The "Amount to be billed" value displayed in the Debit memo-request is showing the right value (based on the open item value captured for the WBS Element, DIP Profile settings).

-thanks