It was written poorly. Usually directions for another size are in parentheses right after the original direction.
You have to take patterns with a grain of salt, just like everything else. Many years before the internet, I made 2 cabled hats from a pattern book, and I still wear them. But in the back there are 14 P between the last 2 cables, whereas there are 6P between all the other cables. I was too green to know how to make a correction. Complaining to the author or a publishing company wasn't as easy as emailing a pattern-writer now.
You can't always "trust the pattern."