In ATL recently, used the app to confirm my rental and see options to change. Some car came up with a mileage figure. Refreshed to see if another option was available, but it was the same car (license plate, space), but with a different mileage. I was intrigued, so refreshed again to the same car, but with yet a different mileage.
When I picked up the car, the odometer was completely different (like 23k while app showed anywhere from 2k to 15k miles). When I returned, I mentioned to the woman and she said, "yeah, that happens a lot." Fortunately, I set the trip meter and told her I had only driven about 60 miles and was, therefore, below the fuel service limit. She just waived the fee due to the mileage discrepancy.