Confused about calories in/out

Your BMR is not your net. It does not change day to day based on what you eat and how much you exercise. It's your basal metabolic rate -- the energy your body needs everyday to sustain bodily functions at rest -- breathing, heart beating, keeping all your cells alive, etc. MFP calculates it using an algorithm that takes into account factors like your weight, height, age, and gender (although I believe weight has the greatest effect), based on information you provide. Your vivofit, I assume, is a heart-rate monitor. I would assume the 1276 is probably the calories it estimates you have burned for the day while you were wearing it, based on your heart rate and information that you have put into the vivofit, such as your weight.

A couple of terms for you: TDEE is your total daily energy expenditure - all the calories you burn in a day, whether you're awake or not. BMR, as lynn said, is the bare minimum calories your body needs to survive if you were in a coma. Do a Google search for "scooby calculator" and put in your numbers. Your TDEE and BMR are based on your height, weight, and activity level. You should be eating somewhere between those two numbers in order to lose weight the healthy way.

Are you logging your foods and drinks accurately here on MFP? If yes, your gross and net calorie intake on MFP is far, far too low. The consumed number implies you only ate 911 calories throughout the entire day - probably well under your BMR to begin with. Then you exercised, so you got a net of 750. Try to read up on some of the sticky posts at the top of the sections - you'll learn a lot about how to track, what to track, and what all these acronyms mean.

Even though I wasn't looking for this information, it was very helpful/insightful. Thanks y'all, for sharing your knowledge in an easy-to-understand way!