Jack's speed when jumping up

[Toybox]

I would guess he just measured them, letting Jack race against a skeleton for example. (Or jump on a moving platform for vertical speed - this, for some reason, had got me puzzled for a while).

Although... Is the

5

speed of a skeleton the same as the

5

of a skull spider or a moving platform? If I remember well, the speed of a red bird is twice the speed of the blue one.

(Eh, who said I'm obsessed by birds? > )