cable six usually means to slip 3 sts onto a cable needle and hold them to front (or back) of the work. knit the following 3 sts, then knit the 3 sts from the cable needle. Check out the decorative st video section under the Advance Techniques tab at the top of the page. There's a video on cables to give you an idea.
the cable video)
Sorry, I'm not sure about the 12 st repeat. It looks like a 9 sts repeat to me...