Why is a vehicle listed as 1 accident when it has a clean carfax report?

I'm guessing it had an accident but it never got reported to Carfax or the report was altered. Some smashed up vehicles get fixed at in house body shops and resold, thus no records. Others paid cash so insurance and Carfax agencies don't find out. Again no records. Take a good look at the paint job.

There's another reason, by chance is there a number associated with the accident showing? If so, what is it and I'll confirm what it is !