The reset timer button is used when the script has slowed down too much. Each time the script sees a PRE it will add 10ms by default to the timer so it slows itself down. You can change this add time in the options/timer menu. By having the script slow down it will give you enough time to work on your queue and not be bothered with a lot of PRE's. The script at this time has no way of subtracting the added time because it doesn't know if you are working from queue or have stopped. If you notice the elapsed time getting too high then you can press the reset timer button to subtract all the added time so it goes back to the original timer.