Which is correct as long as they are still marked as Unread and or you
haven't refreshed the folder yet after marking them as read.
The lack of detail in your post prevents us from giving us a more direct or
precise answer.
Include at least;
-your version of Outlook (Help-> About)
-type of mail account (POP3, IMAP, Exchange, HTTP, Outlook Connector,
Exchange, other...?)
-any errors in their exact wording as they are presented to you.