Your ranking in your platoon/company etc. is based on your over all score, which is comprised of your academic grades, PT, leadership evals., and peer evals. Candidates do, on occasion and perhaps unwittingly, screw eachother on the leadership evals by not performing for other candidates who are in leadership billets. Peer evals, or "spear evals" are when you rate your squad numerically as a leader and a candidate. Some people get quite bent out of shape when they find themselves ranked near last out of the squad. The best remedy is to keep your nose the grindstone and push onward. I found that I was usually only sure of the candidates I rated near the top and the very bottom. The rest could have been anywhere in between as I hadn't observed enough to place them in any specific order (at least for the first eval).
Best advice: don't worry about this trash, even when you're down there. Give 110% and this will all work itself out.