First, try not to think of yourself as up “against” anybody. The only person you’re competing against at this point is yourself. (in other words, so long as you don’t behave like an idiot at the finalists’ weekend, you’ve got a good shot.) And, frankly, being offered a trip to campus (complete with a stay at the Hotel Capstone!) is a pretty special opportunity - just make the most of it. 
Past posts suggest that some 60 candidates are invited to the weekend, the number who attend may be somewhat less, and some 25 - 30 will be selected:
http://talk.collegeconfidential.com/university-alabama/1866718-how-did-the-cbh-interview-weekend-go.html
http://talk.collegeconfidential.com/university-alabama/1727483-process-for-selection-of-ufe-and-cbh.html
And here’s some advice from @mom2collegekids for those who will be attending:
http://talk.collegeconfidential.com/university-alabama/1286668-tips-for-cbh-and-ufe-finalists.html