alpine lace

Iapos;ve been reading the posts and lurking for awhile now and have learned an awful lot from everyone. So now itapos;s my turn to ask a question. Iapos;ve decided that the next thing I want to learn is socks. Iapos;ve knit everything else from scarves to lace so itapos;s time for something new. However the pattern Iapos;ve chosen gives the sizes as "Small, Medium, Large, 7.5 (8.25, 9)" around." Around what exactly? The book I bought gives 5 different places to measure. I can be pretty sure itapos;s not the length of the foot or the height of the sock, so that still leaves 3 places to measure. Iapos;m so confused. Thanks for any input. BTW itapos;s a toe up pattern if that makes a difference.

alpine lace, alpine kitchen and bath steamboat springs, alpine kirkwood shop, alpine kilns, alpine kicker polk rockford sub woofer.