This is a cute hat, but I wouldn’t recommend it for beginners, even though it lists the skill level as “Beginner”. The cables, wrap-and-turn method for the turn of the brim, and the decreases in pattern are probably a bit challenging for a real beginner. It’s probably fine for advanced beginners or intermediate knitters, though.

Additionally, the pattern is either in error or misleading in the instructions for the Spiral Purl pattern. But it’s easy to fix!

For the Spiral row setup round (round 24), adjust the stitches to 71, 81, or 91, by only decreasing one stitch instead of two for the small and large sizes, or by increasing one stitch for the medium size. Then you can just k4, p1 around and around until the hat body is the desired height. You don’t need to worry about an end-of-round marker.