When i change bit size it auto changes to mm instead of inches

when i change bit size it auto changes to mm instead of inches why is there a setting for inches i missed what is goin on !!!

When you change the bit size don’t hit enter, I am guessing this is when you are adding a custom bit. When I enter the 60 degree v-bit I input .5 then click out of the cell if you hit enter it will change it to mm