I would like to buy Airport Express Travel Pass

1. I am arriving HK at 23 Aug 17 and depart at 28th Aug 2017.
1. Can I use the airport express at my departure day, i.e. at 28th Aug 2017? and
2. I Want to use unlimited option on 23rd Aug to 25th Aug?

or should the unlimited journey starts after the Airport express journey?
Is it possible.