Hi
I found this in the LunuxCNC "Getting started Manual"

• Home Switch Location - The location at which the home switch trips or releases reletive to the machine origin. This item
and the two below only appear when Home Switches were chosen in the Parallel Port Pinout. If you combine home and limit
switches the home switch location can not be the same as the home position or you will get a joint limit error.

Hope it help