The #'s are just part #'s.for example, #2 is far more aggressive than #7 (Showcar Glaze), But # 83 is more aggressive than #81. There is an aggressiveness chart or 2 somewhere in the forums.
If you are looking ath the "80" series, 83 is the more aggressive, used for swirl removal, etc. 80 is a Glaze/light swirl reducer/light protection. 82 Swirl Free Polish is a light polish/swirl reducer and 81 Hand polish is basically a non-abrasive polish used to add depth/wetness.