so in order to lose a pound i have to burn 3500 calories PLUS the calories I've already eaten that day?

Why are you making simple math so difficult?

First off, you need to find out approximately how many calories you eat per day (that does not make you gain any weight).

Let's just say you daily intake is 2000.

If you only ate 500 that ENTIRE day you're 1500 ahead for the day.

If you burned an additional 1000 that day then your total loss that day would be 2500.

Don't forget that you're also going to lose weight while you're sleeping.

Basically, every second of the day your body is burning calories. You eat to replenish your body.

Think of your body like a gas tank. If a full tank gets you 400 miles but you only fill it up halfway you're only going to go 200 miles. But if you have an extra tank (stored fat) you can go farther by burning up that fuel instead of feeding the first tank.

You don't want to lose 1 pound a day. This diet is unrealistic, unhealthy and you won't be able to do it long term. Try burning a pound per week. that way you only need to burn 500 calories a day. Go on a calorie calculator website and put in your height, weight, and activity level, and then it will tell you how many calories you should consume to lose weight

mira amiga te recomiendo que te ejercites cotidianamente y no muy pesado tu organismo se dañara. Evita comer carnes rojas, comida frita y controlar el consumo de azúcar y en menos de un mes tendrás buenos resultados.
NOTA: Has esto durante un mes hasta que tengas buenos resultados y si quieres continuar solo haces ejercicio.