After using stayman, then bidding a minor suit rebid, opener is making a minor suit
slam try. It asks opener to describe her minor suit holdings using the following responses.
3H = 4 clubs (not 4 diamonds)
3S = 4 diamonds (not 4 clubs)
3N = If opener bid 2D after Stayman, this bid shows 4-4 in the minors.
If opener showed a four card major after Stayman, this bid shows no four card minor. This bid makes sense, because opener could not be 4-4 in the minors at that point and have a 4 card major without being 4-4-4-1.
4C = Shows 5 card club suit
4D = Shows 5 card diamond suit
4H = Shows a 6 card club suit
4S = Shows a 6 card diamond suit
The complete description is available in Kearse's book. Source: rKearse's Birdge Conventions Complete: