format is wrong

Hey
I have a self-assembled laser since last week
2.5 W.
Now the drawn sizes are not correct, I have drawn a square that indicates on screen with 21mm and height 21mm, but lasered it is 65x65mm.
My question how can I change that ???

This would be settings in the GRBL controller. You would need to reduce the ‘steps per mm’ counts in your controller by a factor of 65 / 21 (roughly 3.1)

Read here: https://github.com/gnea/grbl/wiki/Grbl-v1.1-Configuration#100-101-and-102--xyz-stepsmm

thanks for help