I went to the plug in site and have been through the settings, not finding anything on how to use. Just basic usage, like adding variations. I'm not sure what is meant by "Value Price" and "Prefix". I already added the price of the item when I created it as a product, is the "Valuse Price" different from that? I assume the prefix is to add or subtract dollar amounts, but when I try to use it I get 0.00 for the total in the cart.