My stats showed a sudden jump for a day this week, and when I checked them, I saw not only that there was a large increase in Anonymous visitors, but there was a corresponding, and NEGATIVE, number for “other traffic”
other = page_view_anon + page_view_logged_in
- page_view_anon_browser - page_view_logged_in_browser
These counts are recorded separately. If browser views exceed the total recorded anonymous and logged-in page views, “Other traffic” becomes negative.
One possible explanation is that someone discovered the browser-tracking endpoint and sent repeated requests directly, increasing browser views without corresponding page loads.