Need simple answers, don't get it??

chell53

I know this must have been asked and sorry if the answer is out there....Fitbit I don't understand Calories in vs Calories out? I do all my logging here on MFP and then if I look at FitBit the arrow is never in the middle it tells me it is low or high....how do I get it to stay in the middle where it belongs? I eat around 1300 to 1400 Calories a day, so to lose I know I should put out more right ? Can someone explain this to a old lady please.....thanks