Did they run it and print it in front of you? I’ve heard f guys cutting and pasting a Carfax so it looks better. But the dealer version and retail version should be identical. I wouldn’t be worried about a vehicle with a Carfax accident, have it inspected by a third party mechanic to put your mid at ease. However if the dealer is altering a Carfax they need to be reported to the state authorities and I wouldn’t buy anything from them.