I think this must be the pattern:
http://www.yarn.com/product/wisdom-y...-free-pattern/
If it's a mistake, it's a consisten one. It occurs in all 3 sizes. That said, I don't see how you can pick up until you get to the end of the row. So knit
20sts, pick up along the left side of the heel, knit 17 instep sts on needle 2, 17sts on needle 3 and pick up along the right side of the heel onto needle 4. Knit 10 of the heel sts from needle one onto needle 4 and you'll have the correct number of sts distributed across the 4 needles.