How many hours should be included in dog boarding?

The last dog I boarded arrived at 11:30 am Saturday and didn't get picked up until Monday around 5pm. The initial stay was for one night but when I did not hear from it's owner 24 hours later she booked an extended stay (which I didn't realize I had put that as an option for her to choose) and picked him up 29 hours later. That means I had the dog for a total of 53 hours and she paid $50.