Should the last travel day be always an inbound trip?

Hi! 

I purchased a "4 travel days in a month" ticket, but my issue is that I planned to be too far from my home country on the last day, so my doubt is:

Can I use my last travel day to take a train to reach an airport to go to my country by plane? 

I mean: is it mandatory that the last travelday should always include a train to the country where I live?

Hope my question was enough clear, 

Thank you!