This was the one place my family decided to share 2 credits instead of using 4. Since my son and I love nachos, my big plan was to order 4 milkshakes (using the two drinks, and two desserts), 2 nachos, and then let my husband and daughter pick whatever entree they wanted and call it good.
When it came time to order dessert we told our server we would prefer to skip it and apply the cost of two of the shakes towards dessert. She was extremely displeased and said it wasn't allowed. I told her that was fine, to just charge us for the two milkshakes OOP, but we still were too full for dessert and wouldn't be ordering any.
She returned with our bill and said not to worry about it...she would make an exception and allow us to use the milkshakes as desserts just that one time. It wouldn't have mattered to me either way, but I was happy it turned out the way it did.