Caving to shallow

Hi all am new to caving i have a 3018 woodpecker its ok for me. But i seem to have a problem. When i set the depth to say 8 mm in easel it only cuts to around 1 or 2mm deep. Any ideas as to why this is or am i doing something wrong possibly in the set up.
Cheers
Ian

You probably need to calibrate your GRBL parameter $102 as the current value is incorrect for your machine.

Hi what would be the value i need to set it at or were would i found this?
I have had a play and the cut is deeper but still not what i have set.

Thank you for placing the youtube video. This help a lot and now have a calibrated cnc.