Whether the clock is on the wind or the snap is based on what caused the previous play to end, per 3-4-3.
The summary one of my colleagues came up with is that for NFHS code, if any of the following 10 things happen during a play - the so-called "major clock stoppers" - the clock will start on the snap or when a free kick is legally touched:
a - the ball goes out of bounds
b - B or R is awarded a new series
c - either team is awarded a new series following a legal kick
d - the ball becomes dead behind either goal line
e - a legal or illegal forward pass is incomplete
f - a request for a charged, or radio/TV, timeout is granted
g - a period ends
h - a team attempts to consume time illegally
i - the penalty for a delay of game foul is accepted
j - a fair catch is made
In the casebook play noted, NONE of these items occurred during the down, so the clock will start on the ready for play. Compare that to 3.4.3 - in situation (a), the down ended because of a fair catch, so the clock next starts on the snap. Likewise, in situation (b), if R chooses the awarded fair catch, the clock would next start on the snap.