Your rate is for 24 hours of pet care, but it doesn't mean you have to stay there 24/7. You might have errands to run, other clients to service for walks or drop-ins. But you should be spending a majority of your time in the home especially at night. There is no "overnight" rate or service. It is boarding or house sitting and both are for 24 hours of care, which includes feeding, walking, etc.
The cats need to be listed with Rover. I did notice that you have a fairly high rate for cats, when they really don't take all that much care. You may want to revisit that rate and have a small, negligible one for the "additional" cats.
From postings on this forum over the years, it isn't unusual for customers to try to slip in additional pets. You have the opportunity to get it fixed from the outset, but I would encourage you to come up with a more realistic charge for those cats, which Rover would bill at $40/night.