How to close opened PO when partial reveived and vouchered

Anyone who could help for this, please...

In a PO line, some quantity was received and had been vouchered.

For the surplus quantity opened, how to close normally?

1. I select "9" when Enter Receipt, then the status updated to 980 which looks a cancelled..

    The PO line status should be indicated normally closed, not cancel.

2. I select "7" when Enter Receipt, "receive and close unreceived", but the quantity could not be changed to 0, when I change it, there's an error message.

Could there some method better?

For example: in one PO line,

Current:          Qty Ordered: 10ea, Qty Opened: 4ea, Qty Vouchered: 6ea, Status:390-400;