Theoretically, the car "could" have zero miles on it, as when I used to work at a dealership, the speedo's fuse was pulled at the factory once it was put into "transport" mode. It was then only replaced during the PDI, so most cars had 0, or maybe a couple of miles on them at most if they had been back down to the valeters after PDI. In fact, last week when I was looking at why the courtesy lights in my Mum's 2014 Hyundai I30 weren't working, I had the interior fusebox lid off, and noticed that two of the fuses were fitted within a pull out carrier, pulling the tab killed power to the radio, alarm, instruments and courtesy lights.... Obviously Hyundai's take on transport mode, which would not reset the mileage, BUT would stop it accumulating if it was at zero, so to speak...
The reason they do it, is to prevent parasitic battery drain when the cars are stood in compounds, sometimes for months, it does work as I've gone to get a car that has been in the storage pound for 9 months, and it's started off the key.
Mike