They are alive and breathe air through the eggs. Yes, keep above the water line. They still need to be near moisture, to be in some degree of humidity to stay pliable not dry out and die.
TMaier may chime in, I can't remember atm, how many days, it varies a little based on temp and whatever else. She has clutches hatching frequently!
One day there will many little tiny ones cruising the glass.
Do not scrub the glass, leave the biofilm grow to give the little ones as much to graze on as possible.