Question about Gen Book example

Those patches labeled p building or those with several patches together (labeled "Step by step") provide a chance to show you how a more complex patch is built step-by-step; it's often the case that the sequence of patches track the illustrations in the book for building the "final" version of the patch. It's generally the case that each further iteration of the patch adds a single new feature, which may mean that those patches have everything you need for your own patching and nothing you don't need....

Ahh got it. Thank you!