34 websites carry this Matomo site id in its source code@if (Model.Total > IdentifierModel.MaxSites) { ; the 200 highest-ranked are listed }. The setSiteId of a Matomo tracker, with its host.
The 34 sites listed on this page: each has the id in its stored HTML or first-party JavaScript. The setSiteId of a Matomo tracker, with its host; sites sharing one are usually run by the same owner, agency or platform.
How was \#2 found?
By reading the stored source. PageSourceSearch keeps the exact bytes of the pages and scripts it crawls and extracts the identifier from the tag's own snippet or meta tag, so every listed site can be opened at the line that carries it.