The data is, as mentioned, pretty noisy. It's a best-effort guess as to which is the canonical RSS feed for the particular domain. There doesn't appear to be any convention for specifying this, so when there's multiple a fair bit of guesswork is involved. Expect a fair number of dead URLs, lots of spam from CRMs that generate uninteresting feeds.
The data is, as mentioned, pretty noisy. It's a best-effort guess as to which is the canonical RSS feed for the particular domain. There doesn't appear to be any convention for specifying this, so when there's multiple a fair bit of guesswork is involved. Expect a fair number of dead URLs, lots of spam from CRMs that generate uninteresting feeds.