Looking for some extra insight on domain authority. Competitor has similar authority with substantially less backlinks

Just looking to hear some thoughts from you guys.

Using Ahrefs free back link checker tool...

Our website has a DR of 28 with 6821 backlinks and 1,031 referring domains.

The competitor has a DR of 27 with 3273 backlinks and 245.

Just curious how we basically have the same authority yet we have substantially more links. We have not paid for any links so we shouldn't have many spammy links, it would be more likely they have done that, because they have kind of just come out of nowhere. Our site has been around longer and some of the top backlinks I've noticed are referring to informative articles my boss has written.

Would this be because the competitor happens to have more back links that are coming from domains with higher DRs? Or am I missing something else here.

Also say there is 1000 backlinks and 250 top referring domains, does that means that off those 1000 links, there are 250 unique domains, meaning there are multiple backlinks to the site coming from one domain? Just want to understand that part correctly.

Results are slightly different using MOZ SEO tool, we get a DA of 34 and competitors is 25. I like that a bit better but still looking at the metrics we have several times the links and ranking keywords than the competition does.