You probably over estimated your physical activity, as that is the only data not based on physical measurements. Include activities for an average number of hours per week. Only include your exercise time based on your average number of hours / minutes per week. The Healthy Body Calculator® is based on nutrition science and calculates accurately if you put in measured physical data.
Congratulations on choosing low-fat foods. It is difficult to eat really low fat and high calorie because of how much more food (volume) you have to eat. The difference between the calories in 1 gram of fat (9) versus the calories in 1 gram of protein or carbohydrate (4) make fat a good choice for people who want to gain weight or are unable to eat a large volume of food. At 3,000 calories per day, you should aim for 130 grams of fat or less. This would translate into 20 fat servings. (1 tsp. butter or 1 ounce of lean red meat would approximate 1 fat serving.) At 5,000 calories per day, you would have to aim for 167 grams of fat or less. This would translate into at least 33 fat servings. While this sounds like a lot of fat, depending on the foods you choose, fat adds up quickly even if you don’t eat food that is fried.