Rule on a batters in the batters box

Question
I have a local asa umpire who keeps moving my hitters back of the plate.  When I ask him why he is doing that he keeps telling me the batters feet are touching the batters box line .   According to him the batters toes or feet are not  permitted to touch the line of the batters box.  Is this the correct ?  I see many batters with their back foot on the back line of the batters box and he never says anything.  But if the foot is on the line next to home plate he will make them back off the plate.  I will like to know the correct rule so he will quit coaching my team.  Thank you

Answer
At the time of the pitch, both feet must be completely within the batters box.  The lines on the softball field are completely within the area they define.

It is ok for the feet to be touching the lines defining the batter box as long as they are completely in the box.

Tom