Hi,
In the above scenario, you have 1 quantity open for MIGO and MIRO (500 (po)-499 (GR), for the 499 quantity GR and IV has happened, so now you can clear through automatic clearing F.13 by scheduling a back ground job on a weekly or monthly as per your business requirement and which is recommended, if not you can clear it manually through F-03.
Regards,
Ravi