You probably over estimated your activity hours as it is the only subjective (your estimate) data. Or you are very overweight and don’t need to reduce a lot of calories to lose 2 lb. per week.
Surprisingly, most people think that 1200 calories are a one size fits all diet for weight reduction. Not true. Depending on what your current weight is and your current calorie intake, you may be able to lose 2 pounds per week on 2500 calories. You would lose a lot more weight more quickly on 1200 calories, but you may be more likely regain quick weight loss or find it very difficult to stick to 1200 calories because it is too low.
Re-try the Healthy Body Calculator®, but this time don’t enter any activity hours. Also, don’t choose to lose weight, just maintain. The resulting calories will be your BMR (basal metabolic rate). Now go back again and include your activity hours to find a calorie level appropriate for you to lose 2 pounds per week.
The Healthy Body Calculator® is based on nutrition science and practice so yes, you can believe it.