Be careful. Even a clerical error on the odometer reading can decrease the car's value by dinging the Carfax. The Carfax could report a "suspicious odometer reading" "possible rollback". It happened to me. With mine it was obvious the clerical error was made when I bought my car and then corrected with a over 60,000 mile increase on the odometer back to the correct mileage (13,678) within the same week BUT the damage was done. Didn't find out about it until I was trading it in four years later. "Suspicious odometer reading" on the Carfax devalued my car by 5K. An odometer clerical error can be corrected by the DMV but it can take some time.
Also, to further emphasize clerical errors: A friend bought a Land Rover and a clerk put in the wrong VIN on the title and it took him months to get it straightened out. So the owner of the truck may be right and very honest but it could also end up being a problem for you.
Check the Carfax first and go from there. Well worth the money IMO.