Each "night" of boarding should be good for up to 24 hours of care, as stated in Rover's guidelines:
https://support.rover.com/hc/en-us/ar...
Typically the timing depends on when you drop off your dog. If you dropped it off at 8 am, you should pick the dog up by the same time on the last day of boarding. Since many people drop their dogs off in the morning, when they are going out of town for a weekend and return in the evening on the last day, the sitter is entitled to compensation for the overage. The sitter may charge you for daycare or even a full extra day, depending on how many hours it is over.
Please note that each sitter here is independent and sets his/her own rates and rules. Some sitters may have an established dropoff and pickup time, which might mean less than 24 hours. Some might also charge for daycare.
The best thing to do is ask the sitter and read the profile because it may already specify times and charges. Sorry but it is not uniform here on Rover. House sitting is even more irregular.