http://www.nodebb.org/ does not have http://www.nodebb.org/favicon.ico
Since this is not apart of the git repo I am posting it here. I assume your logo's "O" should be the image.
Same on Persona theme with Yeti skin
Look at the number of notifications. What do you see? - Yes, there is -10.
As it turns out, if you very fast click on -
Even if you simply click on a few laps they stray from the correct number.
I am only able to reproduce this if the "non-fluid" container is active. Fluid (100% width) view does not do this at 67% zoom.
Edit: Ah nevermind, it does happen in both views, just on smaller browser viewports.
Edit: Only seems to happen in Lavender.
Check this one, more about.....favicon
https://github.com/designcreateplay/NodeBB/issues/1290 should be fixed.