There is no discount.
The conditions for being able to do this were to have either an AP rate room reservation or a full price room reservation. You couldn't do it if you were using some other type of discount offer or package.
It is referred to as a ticketless AP package with dining (or something similar with all those key words in it).
Like other dining plan situations, everyone in the room must have the same plan for all the nights of the reservation. The only difference is that you don't have to purchase tickets from Disney.