New settlement amount after the reversal.
To send a full reversal, the new SettlementAmount should be set to "0". The entire transaction will then be reversed, and the original transaction should not be settled with the FDMSSettle component. If you wish to reverse only part of the transaction (known as a "partial reversal"), simply set the SettlementAmount to the new total, minus reversal amount. For instance, if you have a $25 transaction and you wish to reverse $10 because one item was not in stock, set the AuthorizedAmount to "2500" and the SettlementAmount to "1500", and then call Reverse to do a partial reversal.
Note that partial reversals may not be performed on partially authorized transactions. If the ApprovalCode starts with "AL" and the Response.AuthorizedAmount from the original transaction was less than the original TransactionAmount, a full reversal must be performed with the SettlementAmount set to "0".