The additional $1 is the Payment Gateway's process of tokenising the credit card. It is held as a pending charge for seven days and then will be released. It is a similar process to when a hotel or rental company holds funds on a credit card.
Tokenising the card encrypts the details of the card so they they can be held within Payments2Us for future payments, without having to keep the CC numbers and expiry date . CC details are kept securely in the Payment Gateway, but are not held within Payments2Us for for security purposes.