im brand new-can someone help explain the stop countdown?

im brand new to minecraft servers and general and the stop timer doesn't make sense to me. do i need to start it for anyone to go on or will it automatically start if anyone joins? if not is there a setting i can change or a way that other members can start it without accessing the settings? thx.

so if someone joins the timer automatically resets without me having to access aternos at all? ive had a couple people who couldn't join from it shutting down and when i clicked start they were able too get on, am i doing something wrong?