Stars A1 Maid Service

I bought their 2 3-hour-session coupon on Groupon. It's $55. And every time you have to leave $17 taxes and gratuity. I don't understand how they calculated it... They don't provide any cleaning equipment. For the first time, the cleaning lady left 15 minutes before the 3 hours ends, that's fine. But the second time, another cleaning lady, she left half an hour early.. I said, "There is still half an hour left." She said, "So what."