HI jd,
The more calories you burn the greater the calorie deficit will be on your dashboard. It may look like Fitbit is telling you to eat more but in reality what it is suggesting is that you "could" not "need to" consume more calories and still stay within the target zone for your goal.
Your target zone is based on your overall goal and given your choice a calorie deficit will be recommened. If you maintian your calorie deficit daily you will "in theroy" reach your goal in the time frame you originally setup. If you find that you are continously burning more calories than you consume and have a large deficit than you may want go back and modify your food plan. There is nothing wrong with reaching your goal earlier so leave it where it is if your want. But remember to strive for a balance, you want to keep your metabolic rate engaged. If your body thinks you are trying to starve it, it will lock (figuritively speaking) your weight and actually prevent weight loss.
