Partner's 2NT rebid = 18,19 balanced
You have 18 balanced..... >> 36, 37 combined.
So, we are possibly off an Ace.
If we have all the Aces, we are missing a K or a KJ or 2Q or Q & 2J or Q & J.
I was Responder and just bid 6NT.
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1NT = 15-17 hcp
1any, 2NT-jump rebid = 18,19
2NT open = 20,21
2C, 2NT rebid = 22-24
On any of these Notrump bids, I reserve 4C-jump as Gerber which could determine if missing an Ace, however, I felt the prospects of a grand would be less than 50%, whereas we should be cold for 6. Partner's only long suit ( 5 cards ) would have to be a minor.