Seats on the bus are reserved in the order of arrival, so if you want to sit in a fixed place (e.g. first row, last row), then reserve a fixed seat!
You can buy one of these at a time, and your fellow passengers can book the rest after registration.
Price: €10/person
After booking your package, you can find and book it under extra services. Once you have entered your booking, you can book it later (until the service is sold out).