Okay. Explination tiemz.
A "Deadzone" is the representation of your accuracy for the way you play. Depending on your playstyle and your deadzone, you can do really good, or really bad. I don't exactly know which is which, but if you like using guns that are good for close and medium ranges, and are adjustable to all types of styles (camping, rushing, etc.), then you can leave your Deadzone at 10 (default)
I leave mine at the default setting.