The cast on 1 st is to help make the thumb sts a little more flexible. So, knit partway across (29 sts) then turn as if you're at the end of the row. Knit into the first st on the L needle, but leave the st on the needle and put the new one on too. Then knit 14 sts which includes the new one. Turn again and knit only these 14 sts to make the thumb.
sue- knitting heretic