IF anyone tryed this you may have realised my mistake.

For some reason z-offset on my printer calibrated via printrun never seams to work out and has left me with this calculation
Zo = Z Axis Offset,
HbT=Heat bed cover thickness (glass etc)
Dos = Default Z offset (as base set in marlin! (0.5)
Hoh = Hight of head that stick out of hotend,
pr-off = Printruns returned offset. dunno why this works but for some reason it does.

the /10 is required because the first 2 are in mm and needs to be in 10th’s of a mm.