Can't set BLTouch probe offset in Marlin TH3D V1.R2.10d

Can't set BLTouch probe offset in Marlin TH3D V1.R2.10d
When I go into Control -> motion -> probe z offset the maximum negative value I'm allowed to input is -4.975 but this still leave the print nozzle approximately 8mm from the bed.

Does anyone know what's going on?
Why can't I set the probe z offset?

Everything else with the BLTouch installation is working. I'm not sure this is the correct forum so if not apologies and please direct me to the correct forum.

Thanks all in advance.

TH3D is not marlin anymore.. you need to ask in their support forums. [forum.th3dstudio.com]

THanks Dust