You don't get in and they charge you for the meal anyway.
The hard truth is, if you are not in the park when it closes to capacity you cannot get in for an adr...even if it is a prepaid one.
Now there are "levels" of closures, don't know them all. There is a level that allows onsite resort guests access while denying offsite patrons. But I don't know the rest.
Then obviously the big one....no one gets in.
So if you are concerned you need to be in the park before you are expecting it to close.