For example, one of my subscriptions is Hacker News (http://news.ycombinator.com/rss). If I 'mark all as read' then the unread count goes to 0 and all articles titles appear in plain text, as expected. 10 minutes later the unread count is now 4. Click on that subscription and there is now maybe a dozen or more titles in bold text - and not just the top dozen (the most recent) but randomly spread out.