Here is where I am now: I have the session variable (that is supposed to be passing an amount, ANY amount) set to echo the "Discount" column. That works fine. So, in this case, the "Discount" column and the coupon session variable are both 50. Neither is passed until a discount is added to the cart.
So, on the confirm.php page, I have a DA Update record behavior set to add (or subtract, I have tried both) the session variable amount to the Visitors table. It is not passing.