There was a time where arcades were just lousy with fighting games. Killer this, Street that, and Mortal something else. All different, yet all sharing traits. One that was shared by a lot of games is the six-button control layout. Three punches of varying strengths and three kicks of varying strengths. All laid out in a 3x2 block.

But it's tough to keep things straight, especially when you're trying to tell someone how to do a special move or other.

"Okay, jump in and hit Roundhouse, then hold Back, press Jab a couple of times, then press Forward and Fierce"

People who play fighting games just don't have the kind of time to waste with all those words. So, since several games had the same control layout anyway, some folks used numbers instead.

Using this, we can modify our previous stratagem into this much quicker missive

"Okay, jump in and hit 6, then hold Back, press 1 a couple of times, then press Forward and 3"

Much more concise, especially in the heat of a tournament or training session.