I contend that the distances are only rough estimates to some reasonably close portion of the city or town.
On the interstate that runs through my community, there are two signs for distance to my town. The first says “Swansea 12.” Drive four miles down the road, and the next one says “Swansea 10.” Neither of them are correct.
I also noticed on I95 through Connecticut: “New Haven 55.” Drive 8 miles: “New Haven 50” Those signs were close (about 52 and 44 miles), given the distance from the Elm City.
Maybe out west they’re more accurate.