Air Force MEPS B/F% help?

Well, I went to MEPS last week and for my height im supposed to weigh 175 but the thing is im pretty muscular..They did the tape and I was at 19% b/f and well the limit is 20% for the Air Force. They told me to come back in a few weeks. I been dieting and everything but I really dont have a big stomach...I went to the local fitness center the day after I went to MEPS and they did my b/f differently and got me at 13%. Is there anyway that MEPS can do this?? With the Calipers? Or even with the little device that measures it??