I assume that maximum distance in a day is the sum total a cacher travels from cache to cache in a single calendar date.
Today I see one cacher that has a total of over 18,000 miles as the maximum distance in a day. That's almost 7 times the width of the United States. Yet looking at the caches logged for the day, the cacher never left a single U.S. date.
Assuming a 24-hour day, that would mean the cacher traveled an average of over 750 miles per hour for the entire 24-hour day, and still managed to pick up around 200 caches in that single state.
Obviously something is very wrong here.