Hi all. Am hoping someone can help/advise with this pattern. This decrease row doesn’t make sense to me (but then I am a bit of a novice!). I’m knitting the second size (knit 21) - the bit that doesnt make sense is the “decrease in this manner on every following 3rd row” - a) it’s stocking stitch, so the 3rd row will sometimes be purl; b) even if I do the decrease on the purl row, following this pattern I’d be decreasing at different ends; c) if I was doing the 3rd or 4th size, then I would be decreasing on every 4th row, which WOULD make sense.
Totally confused :shrug:
Thanks in advance for any help 
Welcome to the forum!
You could do the dec every 3rd row even though some of the dec will be on the purl row. You can do a p2tog in place of the k2tog but you want to keep the [I]position[/I] of the decreases the same. You should end with a line of decreases between the knit sts (k21 on this first row but decreasing with each dec row) and the pattern stitch (k1, k4, sl1pw).
That way you’ll be able to get the decreases done within the correct number of rows for your size.