Let me put my oar in....
As I read the pattern, you are starting a multiple of 13 sts + 3 and you are working 12 repeats of that 13 st pattern (13 sts x 12 repeats = 156 + 3 = 159). As you work from row 1 to 14, you are decreasing the sts in each repeat from 13 to 3. When you end row 14, therefore, you should have 39 sts (3 sts x 12 repeats = 36 + 3 sts = 39). So far so good.
On the Next Row, you are going to k3 and cast on 10 to return to your original repeat of 13 sts. You will do this 12 times, ending with k3. That will give you your 159 sts (k3+10 Co = 13sts x 12 repeats = 156sts + k3 = 159).
I hope this works! Good Luck!