Sep 23, 2015 - 5:16 PM
It's valid for up to one month actually. You can use your outbound trip up to a month after the inbound trip. And you'll get a 50% discount on all days in between (just one in your case). It's all explained on the first link I gave you (click "How to use"). Note that I am talking about the Combi variant.
Last modified on Sep 23, 2015 - 5:17 PM by Arno