A loop (repeat, for, for each) happens in a single tick (in a single tick, the actions get repeated as many times as required).
The wait 1 second action will delay the execution of the "add 1" action without blocking the rest of the execution of the page (and so the rest of the loop too).
Here if what you want is for 100 seconds, each second add 1 to the variable, then what you need it to "wait loopindex seconds".
For each iteration of the loop, it will wait more and more (according to the loopindex which is the current iteration of your loop).
Oh, and for a fadeout of opacity, you should rather use lerp(object.opacity, 0, 0.5*dt) (the object will disappear in a second)