Best Answer
Fitbit Product Experts Alumni are retired members of the Fitbit Product Expert Program. Learn more
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/
Best Answer