hi, i have been wondering how many kcal i burn by walking 20k steps i'm 6 feet and 170 pounds. by using the iphone motion, Fitbit says that by walking 20-25k steps a day my daily intake should be around 3-4k (wich i found incredibly innacurate) meanwhile myfitness pal says 2900-3k wich one is correct? does walking at 4mph…