You are paying a fixed rate to order basically whatever you want from the menu!
Now, there are allowances...
Yes, SC does appear to be about $4 max
CS...entree (w/ side if included), dessert & drink choice; prices irrelevant
TS...appetizer, entree, dessert, drink, tip; generally prices irrelevent
all taxes included
no alcoholic beverages included
there are some exceptions.
check out the sticky---
DDP FAQ, and it lists them
you can also find sticky w/ a list of snacks that you can buy. It is a lengthy list, but you will get a good idea what you can buy.