As usual, Stefan is correct. One minute of angle, or one sixtieth of one degree does work out to be about one inch at one hundred yards.One mil or milliradian is an angular measurement of 1/1000 radian which is about 3.6" at 100 yards.As far as sighting in your scopes, the clicks are not necessarily an accurate means of adjustment as they may not be consistent on one scope and certainly not the same from scope to scope. You need to get into the higher end scopes for clicks to be accurate. Figure they're a rough approximation and sight in your scopes accordingly by trial and error.