09-30-2016 20:45
09-30-2016 20:45
09-30-2016 23:59
09-30-2016 23:59
Mine used to do the same. I don't think it's a precise science and depends on its interpretation of your movement. As I never use an elliptical I just removed it from the list of things it tracks and now it always reports walking. If you'd like to do the same there are instructions in this help file:
https://help.fitbit.com/articles/en_US/Help_article/1933/
10-01-2016 00:08
10-01-2016 00:08