1200 calories is not an appropriate amount of food for everyone... if one is larger active, they may require more calories.
The app/tracker calculates the number of calories one needs, based on the current age, weight, height and activity level of the individual trying to lose weight, which is the whole point - being able to get your own calorie needs and not have to go by someone elses.
Good for you trying to start off on the right foot! No matter what this tracker says, your goal calorie intake should be around 1200 always to lose weight and 1500 to maintain. And try to remember, while the numbers are important, so it content. Stay away from the fatty treats like oily chips and sugary zebra cakes. Instead reach for some fruit or veggies. While we all know they might not be your number one choice, they'll quickly look tastier and tastier when you see how many apples or how big of a salad you can eat to eat the equivalent of your favorite junk food. Now you don't have to cut out foods completely, cause that leads to folding, too many cheat days, and all together quitting. Instead of half a bag of chips a couple times a week, try a hand full once a week, then eventually once every few, then rarely. It might suck at first, but when you see the pounds coming off the last thing you're gonna want to reach for is junk! Bonné channce!