I have some more information on this now:
• A base umpire is in charge of administering the 20-second clock. That means if a clock is not visible at the stadium (which is not required), a base umpire will keep the time on the field. If a clock is visible, he is in charge of watching for a violation.
• A pitcher stepping off the rubber does not stop the clock unless the umpire grants him time.
• Each pitcher will be warned once for a clock violation. After the warning, the penalty for a pitcher taking too long is a ball added to the count.
• A hitter will be assessed a strike if he is not in the box by the 5-second mark on the pitch clock.
• Time is paused for a pitcher to step back onto the mound if a play has taken him to another position on the field.
It’s worth reiterating that this is an NCAA rule, not just an SEC rule, which means it will be enforced at road and neutral sites, and in the postseason. This is the first year the NCAA has ever mandated a pitch clock. It has been used in the SEC for years, beginning on an experimental basis.