Your BCP gpa is your Biology, Chemistry, and Physics courses and is the most exclusive of your AADSAS gpa's. Your science gpa takes these three into account as well as any other math or science courses that don't fall directly under the heading of biology, etc.
BCP is only biology, chemistry and physics, where science GPA is those plus Math, engineering, and some other sciences (maybe even psychology . . . best to check on the "general instructions on the AADSAS website). i once got an F in an engineering class so my science GPA is lower than my BCP.