Understanding the whole MFP thing

MMG27

Hey everyone, my name is Omar and I started using MFP a few days ago. I love it because it keeps track of how many calories I am eating but now here's the thing. It says I was supposed to eat 2,520 calories a day with out exercise. I was eating that then cut it down to 2500 calories a day then now 2000 calories. I try to do 30-40min of cardio a day but I eat whatever I want as long as I am in my calorie range. Is this ok what I am doing or what should I be doing? I haven't weighed in yet, I weigh in Friday so I be seeing a weight loss hopefully. I read some posts on here that you have to eat more to lose weight but then I had a trainer at 24 Hour Fitness and he said I have to burn more calories at the gym than what I am consuming, so idk...lol...What is everyone's advice on this? Please help me understand this! Thanks!