Even I knew jump 2♠ isn't a good bid, it is another thing, after 4N Blackwood, I found I had no way to answer it in fact.
Their explanations :
5♣ = Rebiddable ♠, 17+ TPs
5♦ = Rebiddable ♠, 17+ TPs
5♥ = Rebiddable ♠, 17+ TPs
5♠ = Two or five key cards, ♠Q --- Rebiddable ♠,♠Q, 17+TPs