When suit agreement has not been reached, a bid of 4NT is quantitative (slam invitational). There are a number of ways to accept the invitation.
4NT quantitative:
-
5♣: 0 or 4 aces
-
5♦: 1 ace
-
5♥: 2 aces
-
5♠: 3 aces
-
5NT: [pick-a-slam]
-
any 6-bid: undisclosed length in suit, suggesting a place to play (pass or correct)