I think you are getting data usage mixed up with space.
If you were to take something to the dump in your car to make more space in your house. Your Odometer in the car would increase. However you would make more space in your house. The more times you take stuff to the dump the more your Odometer goes up. However the space in your house would increase.
It works the same with data stored on your phone or server. If you tell the server to delete something you will create more space but be consuming data to tell it.