In or out of batter's box

[chuck chopper]

Strangely, If you hit the ball with one foot on the ground outside the lines of the batters box, you are deemned "Out of the box". If you are hit by the batted ball with your feet in exactly the same place, you are deemed "In the box"
I do not know any place in the book that describes when you are out of the box (for the purpose of hit by the batted ball). I have to assume it is not until both feet contact the ground outside the lines. One foot out & the other foot airborne is not yet "OUT". I do not recall an earlier thread.