Óscar Fene
Check your ticket carefully: It says valid all day on the route Zürich - Melide. And as far as I can see in my crystal ball, it does not mention any specific train lines or departure times. 😊 The system simply suggested the correct ticket for the specific connection you’ve looked up in the timetable.
Therefore on that day, you may take any train on the specified ZRH - Melide route (just backtracking is not allowed), and also interrupt your journey as you like at any regular stop. E.g. spending a few hours in Bellinzona (visiting one or several castles) or Lugano city. Just the local buses would not be included in that p2p ticket.