For a perfect size for you, the central double spiral should measure the distance between the point where the seams of the armholes & shoulders meet on the top of a blouse.

Latest pdf uploaded 24 August 2010 includes all errata previously noted.

There are useful notes in the KAL on the all weights lace group.

In particular, see the diagram from Foxycrafters & project notes from lynn893 & Marush. Many thanks, ladies!