student agency两个票价的问题

我在https://bustickets.studentagency.eu上准备订票的时候发现每班车都有两个票价，分别是（Special和Flexi），两者究竟有什么区别，我没看出来~~请教了！

【Special】
Cancellation fee: more than 1 hour before departure: 0 %, less than 1 hour: not possible
Rebook condition: more than 1 hour before departure: by cancellation for 0 EUR, less than 1 hour: not possible
Pay in: 1 day (29/04/16 08:51 CEST)

【Flexi】
Cancellation fee: more than 1 hour before departure: 0 %, less than 1 hour: not possible
Rebook condition: more than 1 hour before departure: by cancellation for 0 EUR, less than 1 hour: not possible
Pay in: 32 minutes (27/04/16 18:31 CEST)