Broken search folder that includes all mails from other search folders
This seems to be a regression in 3.34, as I didn't have that issue in 3.32.
I have search folders with this structure:
The parent search folder (the one with 163534 unread mails) simply includes all mails from its child search folders ("flag" and "non-lu"). This is using the "Matches all" rule (translating from french, sorry ;-)) and restricting the sources to only these two search folders.
Clearly, with 2 unread mails and 18 unread mails, there's no way to reach 163534 unread mails.