Calories

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I have my Fitbit and Mapmywalk app synced with MFP. Yesterday I went for a walk and MMW estimated I burned around 100kcal and my Fitbit estimated around 300 kcal. (I can't remember exactly), but isn't my MMW calories counted in my Fitbit calories? So wouldn't my Fitbit calories be MMW+Fitbit together. I wouldn't add them both together would I and say I burned 400kcal all together?