Amount to be charged from (or refunded to) the card.
This is required for Sale, AuthOnly, Refund, and Force transactions. It is optional or ignored for all others. The transaction amount may be up to 11 characters in length, and must be in the format "DDDDDDDD.CC", and be left-justified with no fill (eg: "1.99"). This must always be a positive, non-zero value.
Note that the TransactionAmount should include any GratuityAmount and/or TaxAmount. For example, if the sale price of the transaction is $10.00, and the tip on the transaction is $3.00 (for a grand total of $13.00), the TransactionAmount property should contain "13.00" and the GratuityAmount property should contain "3.00".