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.