Well, this isn't vBulletin as most are used to for forums.
I know ECF has two "new" features, one is highly modded to only show certain results and the other is less so, but time-dependent.
Here, I believe it's just a timestamp thing as well as unread.
New posts = new AND unread
Recent - All recent posts, whether read already or not.
Anyone notice this on the right-hand side and top:
http://vapingunderground.com/find-new/posts?recent=1
That allows you to quickly and easily see all recent posts, not just the unread ones. I like it for finding recent stuff without searching.