There are a lot of factors that determine how many of each size diaper your baby will need. Each baby's weight, shape, size, and growth rate are unique. You'd be the best judge according to your baby's needs.
My son’s weight is only in the 5th percentile, so I know that these charts can’t predict the weight of every baby. You’re child’s build will have an awful lot to do with how a diaper fits, too. That said, I think the growth charts are a way to form an educated guess about how many packs of each size diaper to stock up. If you’re kid is in the 25th percentile for weight rather than the 50th, for example, just substitute that info for what I have here.