Losing weight while training for half marathon

Hi,

I'm 16, 5'3.5 and weigh about 125-126. I know that this is a completely healthy weight but I'd like to lose 5-10 pounds. I'm training for a half marathon in October and I'm training three days a week. Tuesday easy run  of 4 miles, Thursday, speedwork 4 miles and Sunday long run. My miles per week increases by 10% every week. My longest distance yet is 7 miles. On the other days, I do NROLFW. I'm in stage 3 and I do that three days a week, usually lasting around 35-40 minutes. So I have one rest day a week.  It used to be very hard for me to lose weight. I used to eat between 1500-1600 calories a day and the scale did not budge. But I did some research and found that it's important to eat more to up your metabolism. So instead of following what CC says as a target calorie goal(which was a crazy low number of 1200, ugh) I used this calculator http://www.runnersworld.com/tools/daily-calories-calculator. It says that I burn about 2400 calories a day. So in order for me to lose a pound a week I should eat 1900 calories. Does this sound accurate for me? Should I be eating more or less? 

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