When you buy bonelessl and skinless, sometimes you'll see a small portion of fat along the edge of the breast or near the thickest part. That's probably what they are counting. However, there still is fat in small amounts across the top and probably in the fibers. If you boil the chicken, you will see white fat residue float on the water. That's one way of eliminating it. Why do you really care so much about 4/5% fat? You're body won't even absorb that most likely if it makes it past the cooking process..