When it says "now", how "now" do they mean? I've refreshed a few times and the number hasn't changed (171,533). I went to cisa.gov (disabled all my blockers) but the number here is still the same over here.
While I was looking at the data, the ranking of the top visited pages changed without reload, so I assume it is streamed in real-time. But I guess that the real-time data comes from aggregated and somewhat delayed data.
If you open up DevTools and look at the requests, realtime.json contains a "taken_at" property which shows that the data is updated every five minutes.