The play clock will last either 40 seconds or 25 seconds based on what happened in the previous scrimmage down.
The play clock forces players to play the next scrimmage down within 40 seconds or 25 seconds.
Most of time, the play clock lasts 40 seconds. The offense has 40 seconds to snap the ball and play the scrimmage down. A penalty called Delay of Game will be given to the offense if they don't snap the ball in time.
Sometimes the play clock lasts 25 seconds. The reduction of time from 40 seconds to 25 seconds happens if any of the following situations happen on the previous play: