From my experience, CarFax reports mostly on the mileage of the vehicle.
But they don't know the difference between KM and miles....
My old 97 F150 was a Canadian truck and imported to the states as a used vehicle. It had 99,000 KM on it when imported and CF reported that as MILES.
When it was imported, it had it's instrument cluster switched to one for MILES and the odo was adjusted accordingly to approx 61,000 miles.
They showed me the import and the certified paperwork and I bought the truck.. I traded it about 13 years later and that same CF trail followed it. The dealer asked about it. I showed him the paper work and they took the truck in trade.
CF to me is a waste, but some swear by it, so there you go..
It's always buyer beware whether you trust an internet source or a trusted mechanic or whoever...
Just my opinion of course.. :)
Mitch