As I understand it, commuting is defined as going to/from work or school. So that's what I am counting as my commute miles but I also include detours for errands or appointments. For example, if I go to work, then to the dentist, then home from the dentist, I would count all those miles as commuting. If I ride to work, then take the bike to the LBS over lunch, and then back to work, then ride home after work, I only count the miles to and from work as commute.