the 13 to 15% range is still a very flat stomach, even showing the abdominals when flexedDon't think anyone is having expectations of him or others on this forum to be under 10% BF.
10-12% BF for those who want to be as fit as possible without compromising long-term health
13-15% the optimal level for a man without aesthetic aspirations.
actually even up to 18% is a flat stomach