I'd knit a few rows and then measure again. I haven't done a lot of lace, but I found that when I make squares that need to be a certain width, the cast on measurement is not really accurate, since it gets wider.
"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