That's the problem then. When you use the slip knot, you should knit it. It counts as a stitch.
Try the other way. Just put the yarn over your needle with the ball strand on one side and the tail strand on the other, set your hands and start casting on. The first loop will not have a stitch under it, but treat it as a stitch when you knit.
"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