Node Incrementing

I love the module. Here is the issue I am currently having. I have a user that purchases a node and their pay-per-node count goes to one. I then purchase another one, and nothing happens. I was a little confused, but this might shed some light on it. I purchased a quantity of three of the same node for the person that already has a qty of one and it adds TWO to their amount. I am guessing that the code changes the amount to the quantity, rather than adding the quantity to the total.