We just went through that on a rental 65. Obviously no one at AGCO has ever tried to set one up according to the book. We were setting up for beans. Just guessed at .5" and settled around .43" The readout is in inches. I would think around .8" on corn would be a decent place to start.
We are running at 0.65 for beans and it works well, haven't done corn yet but when setting up there is a menu in the Fieldstar i believe to give you an approximate setting, hope this helps some.