Hello Rithinoi14
If you want to purchase a discounted (½) Supersaver ticket, you must be in the possession of the Swiss Half Fare Card, and this latest when you use the ticket.
If you travel with a Supersaver ticket without having the Swiss Half Fare Card, the ticket inspector will ask you to pay a hefty surcharge.
If you do not have the Swiss Half Fare Card (which is strongly recommended if you stay a few days in Switzerland and plan mountain excursions), you can and must purchase Supersaver tickets at full fare (1/1).
Kind regards,
Roland