Screen Time counting music apps while locked

okay so im really confused about what is considered screen time? i use spotify and its included in at least 2 or 3 hours of my screen time a day. i cant tell if that means the app was open for that long or if that includes when my phone is locked playing music. does it stop counting spotify as screen time when i lock my device even if music on spotify is playing? i use apple music too (but less) and im pretty sure it does the same thing. somebody please explain this !