A Magic Number is the number of consecutive games (or consecutive points earned, in the case of the NHL or any FIFA league), in order to guarantee a playoff spot, division title, or certain seed.
A Magic Number can also be the combination of wins (or points gained) by team A and losses (or points left) by team B. For instance, if Team A's Magic Number is 20, it can be any combination of 20 wins by team A, and 20 losses by Team B. It can be 12 wins by A and 8 losses by B, or 0 wins by A and 20 losses by B.
Traditionally, a Magic Number is used to determine a team making the playoffs. Playoff Magic takes the Magic Number a step further, and shows a teams Magic Number for each seed, whether it's a playoff securing seed or not. Let's use these MLB standings as an example:
In this scenario, the Texas Rangers are about to clinch the AL West. To guarantee finishing ahead of the Houston Astros, therefore clinching the division, they need two (2) wins, two (2) Astros losses, or a combination of a win and an Astros loss. The Rangers already have enough wins to guarantee at least a tie with the Seattle Mariners by seasons end. That means that technically their Magic Number is 1, which is represented by a dash (—). Each sport uses different tiebreakers to determine what happens in the event of a tie, which are listed on their respective pages. The Rangers already have enough wins to guarantee finishining ahead of the Los Angeles Angels and Oakland Athletics, which is represented by an arrow (←).
The Astros still have the possiblity to pass the Rangers and win the division, however they have No Control of their destiny, meaning they could win the rest of their games and it still would not guarantee they would finish first, because the Rangers control the destiny for this seed. This is represented by an "NC".
The Mariners are not yet eliminated from the first or second seed, however they have no control over their destiny for either seed.
The Angels and Athletics have been eliminated from the top three seeds, which is represented by a bullet (•).
In this scenario, you can the Boston Red Sox are leading their division, but can still be overtaken by the Toronto Blue Jays, Baltimore Orioles, and New York Yankees.
The Red Sox Magic Number against the Blue Jays, which would the division, is 6. Their Magic Numbers against the Orioles and Yankees are 5 and 3, respectively. The Tampa Bay Rays have already been eliminated from contention for the division.
# The teams Magic Number
— A Magic Number of 1, meaning the team has secured at least a tie for this seed
← Team is guaranteed to finish higher than this seed
• Team has been eliminated from securing this seed and is guaranteed to finish lower than this seed
NC Team has No Control of their own destiny for this seed