Do another receipt.

doing the second receipt, you are not able to re-select the po since its status is complete...

then they must have completed the line. perhaps they hit "RECEIVE ALL" and then changed to 16 which would have completed the line.

Just jump back into the PO and insert the item again for the missing QTY, then you will be able to receive it.

wow thanks that works,The client had cancelled 16 and received 16... so i have inserted a line with 16 quantities and received them. hope there will be no issue with auditing. thanks