From the pattern:

Sizing for lace garments is very fluid, and can be changed to suit at the blocking stage, keeping in mind that blocking will add more length than width. Size can also be changed as described in the knit-to-fit instructions below. If you knit-to-fit, simply increase or decrease your yarn requirements, according to the percentage you adjust the finished bust. e.g. if you were to make the bust 44” wide, rather than 40”, you would calculate that 44” is 10% wider than 40” (44 divided by 40 = 1.1), you would need 10% more yarn – i.e. 17 balls of main color, rather than 15, and 3 balls of contrast color, rather than 2.