Formations are a simple way to stress the defense and create deception. The number system is a great, simple, way to create multiple formations without much learning for your players.
Offensively we are always trying to keep things as simple as possible for our players. This holds true in the creation of our playbook but also our formation system. We want to be able to get into as many formations as possible while limiting the amount of learning for the team. We found the easiest way to do this is through our number formation system.
The majority of offenses, especially ours, rely on moving one person around to change the formation. In the spread to run system this is normally the H-back because this player normally has a very diverse skill set. We decided that instead of creating a different named formation for everyplace we want to put the H-back, we would just tell him where to line up through our number system. The rest of the offense would base out of our four formations.