Ok - that makes sense! I think I'm just past that part so I'll have to see when I get home.
I casted on for the XS because that's the size that fits me in their patterns. I'm sure I'll lose the puffiness because my arms are big at the top.
Now I have to decide if it's worth frogging it.
Thanks for the kind comments!
randomsnapshots - there are probably lots of different ways to get the sleeves to puff more. What I did was CO for the medium size, and follow the medium instructions right up to round 36, then switched to the small. So I did the sleeve increases and neckline of the medium, and sleeve decreases and body of the small. This does change the stitch count a bit, on mine the body is 4 sts bigger, and the sleeves are quite a bit bigger (I had to work in a few decreases right before the ribbing, because they were a bit too loose).
The only thing is, it won't be exactly the same if you do that with the small and extra small, because it looks like the sleeve increases are the same for both sizes. I have a theory that the larger sizes of each increase "bracket" are the sizes that lose the poof - so the extra small and the medium would be least likely to lose the poof. Just my crackpot theory though.
The sleeve increases happen on round 8 if you want to tinker with them. (They're the crazy k1f&b&f&b sts.)