A profile is considered used only when you get analytics for it. This happens when you navigate/click a link to: Compare Groups, Analyze Profiles, or when you receive a Report for that particular profile.
After a profile is considered used, it can be used multiple times without counting again toward your monthly plan limit.
Therefore, adding a profile to a group means the profile is still unused.
Find out which profiles have been used by whom under Settings > Plan and Usage.