I'm using the SIM gateway to submit purchase transactions. One of the fields provided by the API is x_discount, which supposedly can be used to indicate a discount from the merchant. But the hosted payment form that shows up doesn't actually display the value of the discount I submitted. So the result is that the listed items + shipping + tax add up to a larger amount than is indicated for the total charge. Am I doing something wrong? Is there someway to make the payment form display a discount that is taken off the total charge so that everything on the form adds up?