It is just the difference in how many calories you burned and how many you ate during the day. You want it to be a negative number so that you are eating less than you are burning. That is what will lead to weight loss.
These links might help - the first explains how the calories ranges are calculated and the second is the link to the reports. Is that where you found what your differential was? www.sparkpeople.com/resource/calorie_calcu
Does that answer your question?