I think you are right. Tom says that there is a bike shop 45 miles north of their next destination. Nelson tell everyone their next destination at the very end of Chapter 19, so Tom and all of them know the next stop.
I mean, I don't think it really matters in the end location except to say that you go north and out of the way and then head south for the last 45 miles. This is if you are using the miles to get to the destination city.