He averaged 6:17/mile. He’s an impressive runner, and has won a lot of stuff before.
The race has some pavement, some trails, a river crossing (or more than one?), & dirt roads, with 4500 feet of climbing.
There are a couple rules to try to even out the field, like mandatory dismount spots for the rides, and a rule what gait the horses can use on the pavement/macadam sections.
For comparison, the Boston marathon record pace stands at 4:46/ mile. of course, that’s a much flatter course. But humans are fast over long distance. The fastest long distance mammal!