Well the formula behind the activity level is the same for all users. But since it is based upon the relative calories burned (set in relation to the body weight), it can never be absolutely exact (because burned calories cannot be calculated with very high accuracy - these values are based upon heuristics). I hope you understand that this is the nature of a athletic comparison system like ours and there's not much that could be done about it as it's not possible to get absolutely realistic values.