Too high of a calorie deficit or fitbit/exercise calculation

So for the past week, every day I pretty much consume between 1200 and 1300 calories. My fitbit says that I'm burning anywhere from 2100 up 2500 calories a day. I'm sure it's reading high, don't know for sure I guess. Just trying to figure out how much I should be eating. It's all so confusing. :indifferent: