PO Finally Closed showing obligation in GL

Hi,

I have a PO with one line 500 quantities, 499 received not billed and one returned and cancelled on the PO.

In the PO Header, the status turned to cancelled and showing encumbrance.

The user wanted to close the case, so went to PO summary and searched for the PO, from the tools>control he had only the option finally close. which he did it.

The result was that the active encumbrance cleared from the PO distributions, but in GL still showing the obligation for this PO even after creating accounting and transferred to GL.

Any idea about how to clear the obligation in GL?