I did the TDEE several months ago and I eat between 2000-2500 calories worth of meal. I heard that you need to consume about 3500 calories to gain a pound of fat. So I know I'm not eating that much.
I think you got everything wrong. Your TDEE is an estimate of how many calories your body spends PER DAY. If for example your TDEE is 2500 kcal and you eat 2600 kcal every day, you eat 100 kcal over your TDEE which is stored as fat. You will gain a little bit of fat every day. After 35 days, you will have gained a pound of fat (35 days * 100 kcal extra per day = 3500 kcal). After 70 days you will have gained two pounds of fat, etc.
This also works backwards: if you eat 100 kcal under your TDEE every day, you lose one pound of fat after 35 days, etc.
Also, all these numbers are estimates. In reality, you never spend exactly the same calories per day nor do you eat exactly the same calories every day.
