Does anyone know how those numbers are generated? e.g. are they one of those outfits that use a browser extension?

Those numbers seem mostly in the ranges I posted back in 2018 (https://news.ycombinator.com/item?id=16633521). But the total views they report at https://www.similarweb.com/website/news.ycombinator.com is way off. I think they report 11M monthly (I can't view the site anymore), but the actual number was 209M in November. There's a lot of bot traffic in there, though, so it's a bit hard to interpret.

Edit: on the other hand, 16% of those 209M hits were by logged-in users, who tend not to be bots, and the ratio of logged-out to logged-in users is always high (I would have said at least 10 to 1), so maybe 209M isn't so far off.