[lycier]

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6♥ was alerted as "Correct back - 3/4 key cards -- 5+♥,11+hcp,12-16 total points".
I know GIB have been improved here,but what's the meanings of GIB's 3/4 key cards?

[ahydra]

It means that GIB has 3 or 4 key cards (and so wants to be in slam). 5C was 0 or 3, it actually has 3, so raises the signoff to six. Similarly over 5D showing 1 or 4, if it actually has 4, it would raise the signoff.

ahydra

[georgi]

The only one weak spot here is if 4NT asking person has 0 key cards and there is 5C reply.

Bidding 5M would be raised to 6M without 2 key cards, but supposedly it won't happen in careful bidding and more likely no reason to ask with zero key cards.

[Bbradley62]

I think OP was commenting that if 5♣ is explained as 0 or 3, 6♥ ought to be explained as 3, not 3 or 4.

[georgi]

Point taken about explanation clearness. Will be separated in next version.