Sorry, I wasn’t clear on that part when I answered. You are knitting from the top down and it looks like the collar is the ribbed part that you are currently working on. You will continue in the ribbing pattern until the point a few lines down where it says “work two more rows in ribbing”. At that point you will stop doing the ribbing and you will continue on with the next set of instruction, still doing the buttonhole row every 18 rows, a total of 5 times.
Does that help a bit more??