timer on top center screen-What is it for?
That timer is the time left for the defense event ends.
Some achievements and dailies that requires you to defend something means that you need to hold whatever you are defending at least until the end of that timer, if they keep attacking then another timer starts for a 2nd defense event.
(and the other 8 elite specs maxed too)
If your referring to the item at the very top of the screen that would be the tick/score which I’ll post a picture about below. As for timers on things like garrison those are typically called out if there’s a wp because when the timer ends even if it’s still under attack the wp will open for a short time though this is getting changed with HOT. As for why people may call out about the tick timer with things like garri would probably just be saying hold the circle so that you get the points for tick if there’s only like a minute left. =)
Oh the one in the center (I was talking about to the right), yes, that is the time till the next WvW score is updated.
(and the other 8 elite specs maxed too)