My guess would be that the state the car was registered in doesn't require any dept. of motor vehicles/emissions inspection where mileage is recorded on the spot and/or the car was registered (at 10 miles) and has sat unregistered for quite some time.
Nothing to necessarily be alarmed about. If the dealer doesn't have a logical explanation about how the mileage could be so low from one checkpoint to the next or is answering your questions in a weird way then I'd be concerned, but otherwise no. I'd let him know you'd like an explanation b/c the Carfax spooked you and you don't understand it (play dumb). If he doesn't make you feel better then maybe something's up. The dealer should be able to explain how this stuff happens to your satisfaction.
Carfax should report a mileage "discrepancy" meaning at some point the car showed up with less (or identical) miles than the last time it was examined. For instance I replaced my guage cluster several times, each time with a newer, lower-mileage one by chance. My Carfax report explodes with mileage discrepancy warnings. Each time I smog the car they record the mileage (2 yrs) and send it to the CA DMV. When mileage shows less than last time, DMV knows and Carfax knows.
I didn't think Carfax gave accident specifics other than total and/or salvage info.
Remember: unless the police and/or insurance companies were called at the scene (and sometimes not even then) Carfax will show nothing unusual (ex: the car hit a tree, was driven home and fixed at Uncle Earl's body shop.)
Just because Carfax says nothing doesn't mean there's never been an accident.
