She knew how to drive a car and how to brew a perfect Calming Draught and exactly how many pages there were in Hogwarts, A History and which foot to stand on if you were casting shield spells against bombardment versus against curses. She knew how to operate a pay telephone and how to get to Diagon Alley with your fingertips if you've forgotten your wand, and she knew her sister hated her for it. (She also knew how to pretend not to care.) She knew how many times an average witch or wizard could Apparate in a day and how high they'd bounce from, and how to fix them when they didn't.