Finished except for sewing in ends and working out how best to block it.
Sizes (in diameter): small (~22”), medium (~23”), large (~24”)
Surely the pattern means mean circumference not diameter? My head (pretty large) measures 23” in circumference which is a 7.3” diameter using the maths formula that circumference of a circle = pi (π) times the diameter and so diameter = measured circumference divided by π (where π = about 3.14159). I even checked Wikipedia for those formulae in case my memory for highschool maths was flawed and it was not.
I am going to assume that they mean circumference and knit the medium size.