This addon tries to help you protect against fraud. It allows you to place a limit on the purchase amount for the selected payment module if the order is for a new customer. The limit is removed for returning customers. The idea is that if the person is going to place an order for fraudulent purposes, he will probably not do it for low dollar amounts. Once the customer has placed an order, it is less likely that his next order would be fraudulent. This, of course, will not always hold true.