Have you tried hiding and then showing the leaderboard again? Maybe something weird is going on. I know when I tried to sort a leaderboard before, I had to hide it and reshow it for the changes to take place.
Oh and Ammorth is right, that trigger isn't going to do what you want. You need to update the value. Right now you're just setting the value to the Position of the Player + 1. You're going to need an integer variable that keeps track of the count.