A magic number represents the total number of games the division leader must win and/or the second place team must lose before the leader mathematically clinches the title. For example, if the Mets’ magic number over the Braves is 3, then two Atlanta losses and a Met win would clinch first place for the Mets.
To calculate magic numbers, simply take the number of games remaining, add one, and then subtract the number of games the team is ahead of its closest opponent in the loss column.