There are errors in some of the First Edition books’ Charts, including this hat.

From the Book:
You will need a 16-inch circular needle and a set of double-pointed needles in a size that will give 5 stitches per inche in pattern.

These hats are sized for medium-headed women. For a particularly large head, they can be made of heavier yarn (worsted weight, as opposed to DK) at 4.5 stitches per inch. For a child, 5.5 stitches per inch should work in most cases. For a really little one, use sport yarn.