I don't think it works that way. As far as I know, most schools overaccept. So only after the "extra" people give up their acceptances, and that number starts cutting into their usual class size do they begin using the waitlist. So to clarify, the question should probably be: "By how many people does Mount Sinai overaccepts? And how many people on average decline their acceptance to Mount Sinai, causing them to use the waitlist."