Decreasing under arms on sleeves of in-the-round sweater
I'm working on an in-the-round sweater and have the body, shoulders and neckline done. I picked up the stitches for the first sleeve with a circular needle, and the instructions say to "Place marker, join. Working in stockinette stitch, decrease 1 st on each side of marker every 4th round 15 times."
My question is this: how far from the marker should I make the decreases on each side, and do I use ssk on one side and k2tog on the other? If so, how would it look best - ssk before the marker (to the right), and k2tog after, or what?