A refresher for some of you who are confused. Suppose you have the following hand: ♠AJx ♥AK10x ♦KJxx ♣xx. Your partner opens 1NT. You have a quantitative raise with 16 HCP. You could just say 4NT—which tells partner: “Bid 6NT if you are at the top of your range. Pass if you are at the bottom. Make an executive decision—or show a 4-card minor**—if you have 16 HCP.”
However, if you make a Quantitative Raise, you will not be able to bid Stayman. If you and your partner can find an 8-card major fit, you can often make slam with only 30 or 31 HCP, so it behooves you to try Stayman first.
In order to deal with this type of hand, you need two bids: one to ask for Key Cards when partner bids the right major—the one you also have—and a different bid to make a Quantitative Raise when partner bids the wrong major—the one you don't have.
The solution that I suggest for all my students is that, after a Stayman inquiry and a major answer, a jump to 4NT is still Quantitative: “You bid the wrong major, partner. Pass or bid 6NT.” A jump to 4♣ is Roman Key Card Gerber, agreeing to the major that was bid. If you play 1430, the same steps apply, so over 4♣, an answer of 4♦ would show one or four Key Cards in that major; 4♥ would show zero or three Key Cards in that major; 4♠ would show 2 or 5 without the Queen; 4NT would show two or five with the Queen. This allows you to deal with all permutations.
Some partnerships also make the agreement to use 4♣ over Jacoby Transfers for Key Cards, although that is not necessary if you play Texas Transfer.
** Remember the Kantar Adjunct: If your partner makes a Quantitative Raise and you LIKE your 16 HCP (NO 4-3-3-3 and be weighted more toward Aces and Kings than Queens and Jacks), you can bid a 4-card minor at the 5-level. If you and your partner can find an 8-card minor fit (when majors are out of the picture), you can often make slam in the minor with only 30-31 HCP. You must have a ruffing value for this to happen, hence the NO 4-3-3-3 hands rule. On a good day, you and your partner have different doubletons, and that brings in the extra trick that you need. If the NT bidder makes that 5-of-a-minor bid, Responder can: (1) correct to 5NT with minimum and no fit; (2) bid 6 of minor with a fit; bid 6NT if Responder had 17 HCP now that Responder knows Opener has exactly 16 HCP.