Hi bojibridge, welcome to the forums. Congrats on your progress so far; that's no small feat!
Regarding the calorie discrepancy, my guess is that your nutritionist put you on an amount that, given what you burn in a day, lets you lose at a safe pace of 1-2 pounds per week. It takes 3500 more calories burned than taken in to lose a pound. Also, the smaller and older you are, the fewer calories you burn. Many of the people who stick to 1200 calories a day are likely shorter, older, and/or weigh less than you, so that may be part of why you see that.
For example, I'm 43, 5'2", and 105 pounds. FitDay says I burn about 1550 calories a day. I'm in maintenance right now, but if I were to try to lose, if I ate 1600 calories, I wouldn't get anywhere. I'd have to take it down to 1200 or so to get to a loss, albeit a slow one. The closer you get to your goal weight, the harder it is to lose, and that is one reason you will see lower calorie amonts.
It's also important to get to know your own body. There's a lot of variation and you will find the number that keeps you satisfied and lets you drop the pounds as well. Start with where your nutritionist put you and if it doesn't seem to work, ask to revisit it. Good luck to you!
And now that you don't have to be perfect, you can be good.