it appears that when the notifications bell count is updated the number is incorrect.
I see for example 215, while I have just a few unread notifications. Other users reported 234 as the number they see.
Yeah this has been reported on Discuss too and it's a very 🥷 issue. I will try to look into this again soon.
This is done in flarum/framework#3543 and will be part of v1.5 of Flarum.