Could the propane man been trying to cheat me AND GOT MIXED UP?

My propane tank is empty when the guage shows 15%. It was empty. Today I had 75 gallons delivered and the guage showed I had 65%. HE acted weird and said yep that was right!

Gauges in propane tanks are notoriously inaccurate. For example, 15% is not empty, zero should be empty. The amount you receive is measured by gauges on the truck, not the tank.

Watch him fill the tank. He will open a valve to let gas out to make space for the liquid, then apply the hose. There will be a few minutes when no vapor escapes then a lot of vapor blows and he cuts it off. That happens because the tank is full and it's running over. As long as you see that vapor escape before he turns it off, the tank is full. If you don't see the vapor blow out it's not full yet and if he's charging for a full tank, you're being cheated.