The specific numbers work as such:
Jump Z is the initial speed, in UU/S, of the character.
Acceleration due to gravity is measured in UU/S^2, which is a change in velocity.
A handy equation from projectile physics for determining an object’s position/ velocity along an accelerating trajectory helps here:
Vf^2 - Vi^2 = 2as
Where Vf is the velocity of the object at the measured point in time, Vi is the launch speed, a is acceleration due to gravity, and s is the displacement of the object.
You want to move the character s units into the air when his velocity is 0 (no vertical speed, the apex of the jump), so you solve for Vi:
Vi = sqrt(-1960*s)
Plug your desired jump height into “s” and solve for the Jump Z velocity.