Hi lizteston,
Congrats on your weight loss! You should be very proud!
To better help you understand calorie gaps, they are simply calculated from your current weight and activity level, designed to help you lose weight. As your weight decreases, your body requires less energy (calories) to function throughout the day, which means you have to create a caloric deficit through diet and exercise in order to continue to lose weight.
A caloric intake of 1200 calories and walking 72 minutes may seem a little excessive to you. However, it is only for a period of time until you reach your weight loss goals. Additionally, it is very important that you make sure that you're performing strength training in order to maintain/increase lean muscle mass while you're losing! By decreasing fat mass and building lean muscle, you'll become more metabolically efficient. This is sooo important b/c muscle requires more calories to function than fat, and therefore you burn more calories all throughout the day, even at rest. You can see, then, that even at a lower body weight, the more muscle mass vs. fat mass you have, the more calories you'll require. This will off-set the need to continually reduce your caloric intake and increase your exercise.
I would also like to encourage you to increase the intensity of your workouts. By doing so you'll be able to burn more calories in a shorter amount of time. While walking add in 1-2 minute bursts of jogging or running, add elevation or hills, etc. Try to continuously jog for 5 minutes and then recover and repeat. Try incorporating a variety of exercises such as hiking, taking a spin class, or joining a local Boot Camp! Keep your body moving, challenged and motivated!
Best in health!
Kelli