zoomed out = camera view zoomed out as much as possible
+1 = zoomed in +1
+2 = zoomed in +2
+3 = zoomed in +3
and so on..
There might be some difference how u much you zoom in between F1 and F2 views, but i have always jumped with F2 and when the view is +2 it makes takeoff and flying easier

If u dont know how much your camera view is zoomed in or out, you can test it by pressing +/- while jumping.