Yes, he's saying just make the pilot holes a bit larger. Does your drill have a "max" above 15? My Ryobi goes to 15 and the next setting is to not slip the clutch, just have to hang on to avoid twisting your wrist.

I loved the book but my goodness, was it a tough read. Many of the characters are unredeemable and leaves you feeling like you felt when Schindler's List ended. Loss of faith in humanity and just wanting to drink until you pass out.