Problem with size of bone using control rigs and Basic IK

Hello,

I’m currently learning procedual animations.

I’ve created a skeletal mesh from a static mesh and created a skeleton for it.
Applied the bone weights and oriented them.

I’ve followed this video for a start. Youtube

I want that the foot sticks to the ground.

But for some reason the size of the bone “calf” is wrong.
Any help would be appreciated, or some good lecture to learn from.

Here is my Control Rig Blueprint:

My skeleton tree:

The weights that I assigned:



The Control Rig View:

Thanks!