Having another 400-500 calories? That will still help me lose weight?

So I started at 213 pounds..6ft even. I have gone a diet and looking to lose weight and fat. calorie limit per day is 1750. Now I use an elliptical 6 times a week for 45 minutes a day and HR stays in the mid to high 150's. Well the elliptical says for fat loss I should stay within target heart rate ...