Data (steps, distance, and caloric burn) may be duplicated if users wear an activity tracking device while recording a workout with our app. This is dependent on whether or not we receive time-series data from the activity tracking device, which will allow us to "de-duplicate" the workout and activity data. This process subtracts activity tracker data in ranges where workouts overlap it and adds the workout data in its place. Devices that provide us with time-series data include: Withings and Jawbone.
Fitbit, however, does not provide time series data for their activity trackers, so we cannot de-duplicate workouts and activity tracking data. In this case, we simply add the workout data to the activity data to compute the aggregates. This means that the steps, distance, and calories/energy burned on your 24/7 dashboard will include overlapping data from your recorded workouts.
One workaround for this problem would be to remove your Fitbit while recording a workout with our app. This will ensure that no data is duplicated on your MapMyFitness dashboard.
With further questions, please feel free to reach out to us by submitting a support ticket here.