How to map a Discount for an Amazon Invoice (cXml via OBN)

Summary:

We are setting up a direct punch-out with Amazon with document exchange through OBN. We are at the invoice matching stage. All previous processes tested good.

OBN is sending an invoice document with a discount that it not on the Transformed cXml file. There are no errors on the invoice import report.

Amazon will send a cXML Invoice as follows: Total Invoice Amount= (Total of Lines, Freight, Miscellaneous and Taxes) minus the Discount.

The Invoice will go On Hold as the Invoice Amount at the Header does not equal the Total of Lines, Freight, Miscellaneous and Taxes.

How do we map these fields?