Alam8 First, you should define the participants, without any reduction. By default the system shows prices with a Half Fare Travelcard. I agree, this is confusing.
After this, select the timetable from Tirano to Zurich with the right date (I chose May 4th), be sure that it is a relation via Chur and not via Milano, select single journey/1st class, you will find these tickets:
Point-to-point ticket: 164 CHF (this price never changes)
Saver Day Pass: 97 CHF (this price is valid only now, it could change every day and passes can be sold out for the chosen date).
It is now cheaper to buy a Saver Day Pass, but it is not refundable and not exchangeable.