Committed cost is not refreshed based on PO

Hi, 

I do have an issue in clearing commitments for PO in ax 2012 r2.

For an example : User creates  PO line by adding 10,000 Quantity for $10,000 , the commitment cost will be $10,000 once the PO is confirmed.

 if they receive 6000 quantity from vendor and post the vendor invoice for $6000. The commitment cost is $4000. 

Now the users are making the Delivery Remainder to Zero by Canceling the Quantity and not invoicing the vendor for $4000. Therefore the commitments $4000 remains open.

The status of the PO line is changed to invoiced . The user is not ready to finalize the PO line. Can anyone suggest me how to clear the commitment cost $4000 for that Purchase order?