20 sec rule FED 7-3-1

[smoump]

Penalty reads "for failure of the batter to be ready within 20 seconds after the ball has been returned to the pitcher, the umpire shall call a strike. If the batter leaves the batter's box, delays the game, and none of the above exceptions apply, the plate umpire shall charge a strike to the batter".

Should I read this as "if he leaves box AND delays the game? Another words, he can leave box as long as he doesn't delay the game?

Situation: 3-1 count, pitch is a strike, but my timing is deliberate, he begins his advancement to first thinking the pitch was a ball. Once he hears it was a strike, he is already out of the box.

Solution a) he left box, additional strike batter out.

Solution b) tell batter to return to box, 3-2 count.

What do your great minds think!! I personally would do b, but am I miss applying the rule?