Hi there -
The numbers are sitting in the spaces on the weight chart, and not on the lines, because it's reflecting the ounces you have. For example, if you weigh 118.0 lbs, your mark would be on the bottom of the space. If you weigh 118.6 lbs, it would be higher in the little space.
I'll pass on your thoughts about the BMI chart, and it is something we are considering.
Thanks for your thoughts, and let us know if you have further concerns.