Defying the Laws of Gravity

[Freddy]

arevn wrote: ... since the top block is seven blocks from the floor and he's jumping higher than that ...

Small correction. The top block is EIGHT high. And, although not the case here, the top block may be TWO squares wide. Anyway, Jack is

flying

more than NINE high !

But, when Jack is staying on a floor, his jump is as high: just a little more than THREE (starting from ZERO and not from SIX). Why? Because he is always able to jump onto a block of THREE high and not onto one of FOUR high. It is that simple.