4S by GIB East cannot be to play given that opponents hold at least eight spades. And indeed the bidding explanation just says 11- points. It is clearly intended to prevent South bidding 4S. It looks a decent bid to me. However it must be forcing - GIB West can’t pass this bid, which, however, it does, coming off for 4S-7.
GIB west should bid its minor.
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