i dont know the app but i assume he has a core action (-> which he iterates/churns out) and evaluates if people act (-> used as rating) eg (guesses here) new

i dont know the app but i assume he has a core action (-> which he iterates/churns out) and evaluates if people act (-> used as rating) eg (guesses here) new notification types "think for 9 seconds about a loved one" "what was your favorite vacation, go there" if people act -> reward and reuse if not -> reuse less (only by random chance) alternative to notification could be "completed medidation screen"