HH is for the hour and mm is for minutes.
In order to put in 2 hours and 50 minutes type it like this 02:50 You have to put the : colon you can't just use a period.
You don't have to put miles if you put time, but you can put miles instead of time if you know what they are.
As far as activities, I am using the PC version now and have not yet seen how to customize activities. I haven't looked very hard either though.