Dec for Underarm: Work to 4 (4, 5, 5, 5) sts
before marker, BO 8 ( 8, 8, 10, 10 ) sts—38 (38,
40, 43, 47) sts rem. Do not break yarn.
With larger circular needle, work across 38
(38, 40, 43, 47) sts of Left Sleeve, pm, p1, slip
1 st purlwise wyif, p1, pm, work 39 (46, 53, 58,
65) sts of Front, pm, p1, slip 1 st purlwise wyif,
p1, pm, work 38 (38, 40, 43, 47) sts of Right
Sleeve, pm, p1, slip 1 st purlwise wyif, p1, pm,
work 39 (46, 53, 58, 65) sts of Back, pm, p1,
slip 1 st purlwise wyif, p1, pm for BOR—166
(180, 198, 214, 236) sts.
Those are the directions beginning with the last of the second sleeve. So do what it says for the rest of the sleeve part. Then when it says YOKE work those 1st 38-47 (depending on size) on that first sleeve. The first pm, p1, slip 1 purlwise wyif, p1, pm with be right when you begin adding the front stitches to the needle with the sleeve stitches. PM just after you knit off the sleeve sts, and the p1 will be the first stitch you work of the front of the body. Do that little seam section and then knit across the next 39 (46, 53, 58,
65) sts of Front.
I think you will be doing the next seam part (thats the pm, p1, etc. part) beginning on the last of the front based on the number of stitches the front and back are supposed to have-- 42(52, 59, 64, 71). Say if you were doing the smallest size and had 42 stitches on the front and back. The first seam part uses up 3 of the stitches, then it says to work 39 sts from the front. 39+3=42 so you still have 3 left and those would be the seam on the other side of the front. So it looks like the seam stitches are always worked on the front or back sections and never on the sleeves themselves.
Then knit around the second sleeve and right at the beginning of the back section you work the 3rd seam part using 3 sts, work across 39 back stitches (smallest size) and then use the last 3 stitches of the back for the last seam. Then you are back at the beginning of the round which is at the beginning of the first sleeve.