Shoulder shaping bind off question?

When doing the shoulder shaping, I have 20 sts on one side, 23 stitches bound off in the center, and 20 stitches on the other side (separate ball of yarn.)
Now the pattern states, "Shape Shoulder: Bind off at each shoulder edge 10 sts once, then 10 sts once. What does this mean? Wouldn’t you just bind off all stitches?

No, you do the shoulder bind offs separately to make it a little sloped instead of straight across. BO 10 sts, work across to the neck, drop that yarn, pick up the other yarn, and work across to the edge. Turn and BO 10sts, work to the neck, switch yarn and finish the `row’. Turn and bo 10, etc, same as before.

Thank you for the detailed instructions!!! I really appreciate it!