Take a look at the zone map Amtrak provides for travel based on redemption of reward points.

Some cities, like Wolf Point, Denver, Cincinnati, and Atlanta appear to be located on zone boundaries. Which zone do they count as? (That is, do they count "in favor" of the purchaser, so that Atlanta is in the Eastern zone for travel from DC and the Central zone for travel from New Orleans, or "against" the purchaser, so that the opposite is true?)