Their measurements confuse me a little, but I'll explain this so you know.
When following such a pattern that requires measurements listed in the following way:
"To Fit: 31-32(34-36:38-40)" bust."
Bust: 34(38:42)" Length to Shoulder: 21(21-1/2:22)"
9(10:12) oz. of bulky or worsted weight yarn.
You well read the pattern this way:
If you're going with the "to fit" of 31-32 bust, you'll go with Bust 34", Length to Shoulder: 21". And you'll need 9 oz of the bulky yarn.
Same goes with "To fit:34-36", Bust: 38", Length to Shoulder: 21 1/2", and 10 oz of bulky yarn.
Does that make sense?
So let's say you're going for the first one.. (Bust: 34", Length to Shoulder: 21"). You would cast 68 sts onto the size 17 needles. Now, you'll change to size 13's the way Ingrid described and do k1, p1 until the ribbing measures 1 1/4".
Now k1, p1 6 times (that'll be 12 stitches), inc (increase) 1 st (and it let's you know which increase to use, refer to this page
and scroll down to k1f&b), p1. Now you will repeat from the increase(k1f&b) 3 more times. After that is done you k1, p1 the remaining sts.
Now you'll change to size 17's again, keep following the pattern.. if you need any more help, feel free to ask
If I made any mistakes, someone is welcome to correct me :P
Good luck, Claire!