They're basically bookmarks. If you click the 'UserCP' menu at the top left of this page, you will notice a link to 'NZB Reminders'. Those are the NZB posts you have marked.
Note sure right, Tesco is changing/updating the NZB section, it used to be 60 days, I think it's went up since then and with the new board update (soon I hope) will go up even more, watch the NZB section, there will alot of new features and updates coming Including frackin' RSS feeds that work :lol: