Z offset issue

RESOLVED - I reloaded the firmware and it's back to normal now.

I changed the RAMPS board on my printer.

Z offset was set at 1.25 previously. After changing the RAMPS board, now it's decided that it wants the Z offset to be .25

The motion menu on the LCD will not allow me to go below .50

Two questions -

1) HOW did changing the RAMPS board affect the Z offset?
2) Why can't I set the Z offset lower than .50 in the motion menu?

There are config settings in Marlin for the resolution of the Z offset setting process.