Every Kaspa node keeps a book of other nodes' addresses and passes it on. This is what's in it, and how little of it answers.
Every address the latest crawl heard, one dot per 20
Most entries are stale: nodes that shut down, moved to a new address, or never accepted connections at all. The crawler skips an address when the same host or network has just failed it, rather than keep knocking. Answers include our own sensors and other crawlers; Network health counts the nodes among them.
On an average day since 12 Jul the crawl hears 19,800 addresses, and 301 answer. Gaps are days without a full crawl.