53 pounds ago, my TDEE was 2400 at light activity.
Then I dropped 40 pounds and upped my activity a lot, and was being told my TDEE was 2600 on some days (fitbit calculates your TDEE based on how much activity it's registering, your weight, your age, your gender etc etc)
A young person will have a higher TDEE than an older person of the same size and activity level. And then, for even more variation, it's still only an estimate because people's metabolisms can and do vary.
The beauty of this diet is that for five days a week, you learn how to eat like a normal person, eating the calories you need to maintain your body without gaining. THIS IS A CRUCIAL PART OF THE DIET - with crash diets and daily calorie restriction, you don't learn how to eat properly to keep the weight off. Many people find maintenance is harder than losing weight. I firmly believe that this diet teaches you how to eat properly during those five days, so that you won't blow up as soon as you stop. I've been losing slowly but steadily since I started nearly two years ago -- and even when I'm taking a break from fasting, I HAVEN"T GAINED WEIGHT BACK. I'm so incredibly impressed by this, and this never happened with standard BS calorie restriction diets like Weight Watchers.
Then all of the pain, calorie restriction and deprivation happens on two short days. If your TDEE is 2000 and you eat only 500 calories in one day, that's 1500 calorie deficit, almost half a pound of fat!! Two fast days gives you a 3000 calorie deficit in the week, which is close to a pound of fat. And certainly there have been a number of people who have exactly those results for extended periods.
But we're all different. Plateaus are normal. metabolisms are different - even within the same person it may fluctuate month my month or day by day.
The best thing to do is try it the way it's intended. IF it's not working, tweak.
Good luck!