Hertz told me I would be charged if the car wasn't returned charged, I asked how much and they couldn't say. I was also confused because it wasn't clear how to

Hertz told me I would be charged if the car wasn't returned charged, I asked how much and they couldn't say. I was also confused because it wasn't clear how to charge at the airport and that was very inconvenient, I'd rather charge the night before near my hotel. No answer but they said its fine to return it 85% charged. I went out to get the car and the guy said I needed to return it 80% charged. I got in and it was less than 80% charged... wonderful experience.