The default PO Charge Account for an Inventory Item is incorrect

Summary:

When creating a PO for an inventory item, there is a default PO Charge Account that is used. However, the account reflected in that PO is incorrect. The account being used does not appear in the Mapping Sets.

Where can I check the setup that determines the PO Charge Account? From which configuration or source is deriving the account currently reflected in the PO Charge Account?