This is from the Fitbit Help pages. Hope it will help.
HOW DOES ALTA TRACK MY EXERCISE AND ACTIVITY LEVELS?
SmartTrack automatically recognizes and records select continuous movement activities, like running and outdoor biking. If you want GPS data for a hike, bike, or run, use the MobileRun feature of the Fitbit app. For more information, see How do I track my exercise nad activities with FitbitMy Exercise?
If you chose a clock screen that shows a flower, you'll see the flower grow and shrink depending on your activity level.
