There is a discrepancy between payment amount &1 and returns amount &2

What causes this issue?

The "Amount contains charges" field is not activated for the returns
lot edited. The program therefore assumes that the amount entered is
the same as the amount in the payment document.
This is not the case however since the payment document amount is &V1&
&V3&, and the amount entered &V2& &V3&.

System Response

The attributes of the returns line were changed so that for this item,
the amount is viewed as a gross amount (i.e. including charges) and
automatic calculation of charges is disabled.

How to fix this error?

Recheck the details in the document, make any necessary corrections,
and then repost the document.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.