"Corrupted jump boost" - 80 blocks in one second?

I've been making an adventure map in the sky, 50 blocks over void, on flat map "only air". The map is about quick running (speed 20) without jumping (jump boost 200 - "corrupted"). When I fall of, I'm in void (y:0) about 3 secs. But when I try to jump about a small while before I fall, I'm about y: -30 in one second. It is not important, but... It's a bug.