Apple Mail Smart Mailbox shows wrong number of unread
I have a smart mailbox with about 60 messages in it. They have all been read, but the notification, next to the smart mailbox, is 9. I have selected all messaged and chosen 'Mark as Read'. I have also 'right clicked' the smart mailbox and chosen "Mark All Messages As Read". I have restarted Mail.
MacBook Pro 15″, macOS 12.0