knocking off of GR / IR account

Dear Experts,

We had about 89K line items open in GR/IR Account and as per reference of SAP Forum's discussion we used T-Code – F.13 to clear them off automatically. After clearing the mentioned a/c through F.13, there still remains around 77K open line items. But problem is we can not able to knock off those 77K open items. Can you please let me know why they are not happening? and how can we can clear those off?

Thanks in advance and your soonest response will be highly appreciated.

Best Regards.

Ripon Kumar Paul