The true Elo system's provisional system (25 games) is +400 on your opponent rating for a win, -400 on your opponent rating for a loss, then that is added to (your provisional rating times the number of games you've played). Then divided by your new total of games. This site has a rating catch that prevents you from gaining points with losses and losing points with wins. Therefore, it is not a true Elo rating system. For a tie you just take your opponent's rating no adjustments made and add it in.