Enable Negative Adjustments

runner75

I am new to Fitness Pal, and was wondering about the "enable negative adjustments" box. I run 5 days a week burn around 500-600 calories per run. I am linked with my Garmin watch. So by the end of the day, like today, I took almost 16,000 steps. Now My goal is to lose 1 pound/wk, I am set on "active". What has confused me is what amount of calories am I supposed to be consuming? Example today: Goal-1520 Food-1403 Exercise-1573=Remaining a whopping 1690 Calories! Is this number wrong? should I just eat my goal number? Must I disable negative adjustment box? Please help!