I used the clear all unreads shortcut (shift + esc) and it doesn’t go away…
Edit: For anyone having this problem, I’m using GNOME desktop environment and clearing the notifications on the shell removes the bubble on the app icon. Thanks to @EmasXP for the hint.
That’s just basic decency.
I think they mean the left column, where they could’ve just used one big blur to cover them all at once instead of blurring them individually