The numbers between the () are to tell you how many stitches to work for a particular size. In your case, the 8 would be the smallest size and the 9 and 10 would be for the next two sizes.
"Trust the pattern!"
Time flies like an arrow, but fruit flies like a banana.
Hop aboard while we follow the cloud-covered van of knitting harmony, man!! Woooo!! --Hedgehog
IngridKH on Ravelry