Question about non-pivot foot

[drb21610]

I am confused about NFHS's rule 6-1-3 regarding the pitcher's non-pivot foot in the set position. An excerpt below:

"Before starting his delivery, he shall stand with his entire non-Pivot foot on or behind a line extending through the front edge of the pitcher's plate..."


Where exactly does this mean his non-pivot foot is legal? There was a pitcher who started with his pivot foot completely on the rubber but his other foot was halfway in between first base and home and thus his non-pivot foot was outside of the rubber. He then came set by bringing his non-pivot foot parallel to his pivot foot.

This is a balk, right?