Hi,
Just try the following for your posted payment:
1. Search in the application on 'Vendors' to locate the Vendors List.
2. Locate the NOD Vendor. Then go to Manage>>Edit on the Ribbon.
3. On the Vendor Card, go to Vendor>>Ledger Entries.
4. Highlight the Payment entry, go to Process>>Apply Entries
5. For both of those invoices, you need to set the Applies to ID. Go to Process>>Set Applies-to ID and apply payment to both invoices.
6. Once both set the Applies-to Id for both Invoices, go to Process>>Post Application. Review your Doc # & Posting Date for the Application. Click Ok to close out the entries.
That should allow you to apply open documents against each other. If you happen to mess something up after application, from Vendor Ledger Entries, just go to Process>>Unapply Entries. This will allow you to undo an incorrect application. I hope that is helpful. Thanks.