The tires are inflated to max pressure when you received it because it's not loaded etc. so they inflate them to sidewall pressure. That said, it's probably not what you need although it may be. The GAWR ratings are max load weights also. Here's what you do to be safe:
Load your coach as you would if you were going away.
Stop by a Flying J/Pilot, truck stop, moving company etc. and have your coach weighed...each axle. Individual wheel weights are optimal, but few scales have that ability. The weight ticket will be about $10.
Go to your tire mfg website and look for your axle weights.
Use that table to determine the proper PSI for your tires.
If you have any difficulties, return here and post your tire mfg and weights and we will help you. Be safe and enjoy...Dennis