I just bought the Swiss Half Fare Card and added my child (below 16 years old) as passanger. I am now trying to buy tickets but I am not sure how to add my child since they travel for free. When I add passager, there is only the options of no discount, Half Fare Card, Junior-Karte and Kinder-mitfahrkarte. Furthermore, when I click on either of them for my child, the total fare is different. May I understand how this works and how do I buy tickets using my Half Fare Card?