Why do my exercise diary entries ask for the start time of my cardio exercise?
By entering the time you begin your cardio exercise, the calories burned, and the number of minutes you exercised, MyFitnessPal and fitbit.com can correctly reconcile your cardio exercise with the increased activity recorded by your Fitbit during that period of time. Without the start time and the minutes exercised, it is likely that your increased activity level would be accounted for twice: once when you log it on MyFitnessPal, and once when your Fitbit reports increased activity. Entering the start time ensures that your Net Calorie Goal is not adjusted twice for the same cardio workout. The exercise calories you log with MyFitnessPal will replace the calorie data estimated by your Fitbit for that period of time.