You might notice when you check the order overview at the end that there are other seats than you originally chose. This can have different reasons.

1. You chose tickets in a price category that is no longer available. For example, if you wanted tickets in the 1st price category, but there weren't any tickets available of that class at that point, the system will automatically choose the next free category, e.g. category 2. You received a notification about this, and probably just missed it in the hurry of ordering the tickets.
2. You refreshed your browser window while booking or used the back button in your browser. If you refresh your browser while ordering, the system automatically chooses the next available seats for you. Please avoid using the for or back functions of your browser. Simply use the "next" button in the order window.
3. You have exceeded the reservation time. If you need more than 10 minutes for purchasing your tickets, the system automatically releases your tickets and selects new tickets for you.