Net calories

I understand everything about the program but the net carbs. When I generated reports I got 3 different lines for calories. What is meant by net calories vs calories. And which one should I be the most concerned about. I am supposed to eat 1300 for a pound a week weight loss but it gives me 956 (or something) net carbs. I have tried to find some info on this but haven't found it anywhere on the site. Thank you for your help. Toni