I received a reply from Ryan. Apparently, there are in fact over 13.5k single byte differences between the two Proms. The difference tool does not tell you what the differences mean, only that they are there as well as the location address. We, the user, only have access to a small amount of information that we can change. He used the analogy of your computer operating system vs the control panel where things can be added, subtracted or modified. So, in the end, many things may be tweaked outside of our sight, perhaps including the mileage calculation. Rather than burning a new Prom immediately, we will install a replacement of the present Prom first.