[Symmetry]

All manufacturing processes have a certain amount of variability. Binning is the process of testing how fast a given chip can go and sorting them into categories based on that and possibly selling them for different prices based on the category. Apple generally has very few categories but maybe they've got Apple TV rated A9s, iPad mini A9s, and iPhone A9s. There's probably a difference in how many of each manufacturer's chips end up in each bin but unless you're into overclocking it's not something you'll ever have to worry about as a consumer. And I've never heard of someone overclocking an iPhone.