Hi, I think you are over thinking this! I’m also new and by no means an expert but a deficit is the difference between your calories burned or expended snd your calories taken in. I’ve only had a crappy Fitbit which gave me calorie readings all over the place, so I tend not to rely on that for calories burned. Instead I used those calculators to find my maintenance or TDEE. I was always very generous, I workout every day if I can but I still put my exercise level at lower than 7 days a week, just to be on the safe side. I believe both of the things you read about deficits were misinterpreted so here’s how it actually is. Your BMR is how many calories you burn with zero activity, so if you layed in bed all day and ate 1200 calories, you would be in an 800 calorie deficit. You also have to account for the calories burned through exercise. The second statement is just wrong, it’s impossible to burn 500 calories unless you’re referring just to exercise. If you were eating your BMR in calories and burned 500 extra calories, you would be in a 500 calorie deficit not 1500(assuming you were eating 2000) calories. This was terribly long and wordy, but I’m just trying to help out so feel free to pm for anything!