ANSWER: There are a couple of reasons. But first, it may be helpful to know a little bit more about calorie allowances and how yours is calculated.

Simply put, a calorie target is your daily calorie goal or the max number of calories you should eat each day. Having a calorie goal is important because it gives you a target to shoot for so that you don’t over or under eat. Getting adequate nutrition is critical to good health, but it’s also extremely important in weight control. As you probably know, experts believe that weight is largely dependent on how many calories you consume versus how many calories you burn—via exercise, daily activity, and your body’s baseline metabolism.

So, if you tend to consume more calories than you burn, you’re likely to gain weight. Burn off more than you take in, and you’re setting yourself up for weight loss. Breaking even? You’ll probably maintain your current weight.

When you create a Food Plan* from your Fitbit app or Fitbit.com dashboard, you have to enter your current weight and your goal weight. If you choose to lose or maintain weight, you can then pick a plan intensity: Easier, Medium, Kinda Hard, or Harder. This helps Fitbit determine how aggressively to set your calorie deficit—ie: how many fewer calories you need to eat each day to maintain or lose weight.

These calculations are based on the knowledge that 3,500 calories equals about one pound of fat. So to lose one pound you’d need to eat 3,500 calories less each week, or burn 3,500 calories more than you consume. (You can also manually set your own calorie target).

For example, let’s say you want to lose 50 pounds. If you choose the medium-intensity plan, Fitbit will give you a daily calorie deficit of 500 calories, which sets you up to lose one pound a week.

*Always consult with your doctor before starting any weight loss or nutrition program.

Once you choose an intensity, your plan is basically set. But don’t expect your Fitbit dashboard to spit out a fixed calorie target. Although that may seem easiest, it’s not the most efficient way to control your weight. That’s because the key number is your calorie deficit—which doesn’t change—not your calorie target, which can fluctuate with your activity level.

So, instead of only doing the simple math for you (ie: Your calorie target is 2,000. You’ve eaten 1,500 calories. Therefore you have 500 calories left to eat), Fitbit pulls in other data to calculate your Daily Calorie Estimate, a much more personalized and dynamic metric that uses your average activity to predict how many calories you should eat each day.

Unlike a static target, your Daily Calorie Estimate will update throughout the day depending on how active you are compared to normal (assuming you sync your device regularly). So, if you log a killer workout, your calorie estimate for the day may increase. More sedentary than usual? It will suggest you eat less to stay within your goal zone.

To help you gauge whether you’re on track to hit your calorie deficit, Fitbit also provides a Calories In vs. Calories Out meter. This real-time calculation takes the following information into account: your calorie deficit, how many calories you’ve eaten, how many calories you’ve burned, and the time of day. You will be considered in your goal zone as long as you are within 50 calories of your deficit goal for the current time of day.

This is where people can get confused. Because Fitbit is using information in real time to predict whether you will hit your calorie deficit by midnight, it’s possible to see something like this:

At first glance, these stats seem to be contradicting each other. You’re over your calorie target but still have 406 calories left to eat? But what the meter on the left is telling you is that based on your current activity level and the time of day, you’re not on track to hit your calorie deficit.

Using the example above, if you eat your remaining 406 calories, your daily total would be 2,137 calories. Even if you end up burning 2,500 calories—which is still great since it’s more than you ate—it’s not enough to hit your 500 calorie daily deficit goal.

If you’re not into that system, there’s one change you can make to your settings. Click the food tile on your Fitbit.com dashboard and then “See More.” In the Food Plan section, click the gear icon. This is where you can change your Daily Calorie Estimate setting from “Personalized” to “Sedentary.” The sedentary setting starts you out with a low calorie estimate and lets you “earn” more calories by being active throughout the day.

For more tips and inspiration, check out the Weight Loss and Healthy Eating groups on Fitbit Community.