Thing is, what is accurate?
I think your guide has made the knees too low, possibly exaggerated by the confusion of placing it in the middle of a head length because of the 7.5 head length of the figure. In mine, and in ptoing's post, you'll notice the figure is 8 heads tall, and that the knees sit right on the line of the 2nd head length up. Also you are exaggerating the dip of the muscles of the thighs, and the extruded length of them worsens it. The vertical line down the chest indicating the sternum is unnecessary- it is rarely that defined, and if anything would be more defined on a male than female.
If you are going to go for the "average" physique, I believe ptoing's diagram will be of much more help to you than the one from your book.