is:unread
Try doing a is:unread search on your gmail account. Let me know how many archived messages you didn’t read. 
I do this periodically, perhaps gmail should show an unread messages count next to the All mail link, as it does for the Inbox.
yes i did this and it did have a few that were not read but filed in archive by the looks of it as i use outlook to view my emails with and when it dls them i get it to archive it
25, I open most emails.