Using numbers to explain where a defensive end lines up isn’t meant to complicated things.
Those numbers should create a greater understanding of what a player is supposed to do on each play. They also can very quickly illustrate what type of defensive end or defensive tackle a player is because they aren’t all the same. A speed rusher will play one technique, while a more complete defensive end might line up a different way.
The number system starts from the middle and counts out toward the sideline heading both directions. So, the guy lined up over directly over a center is called a 0 technique, while a person lined up to the outside of a tight end is in a 9-technique position, with a lot of other spots in between.
Here is a breakdown of each position and what they’re supposed to do.