Pattern Help: First Sweater Vest

Hi! I’m working on my first not scarf or hat project, a sweater vest!! I bought a pattern on etsy and have the back panel almost complete but am stuck on the shoulder shaping. Would appreciate any help with the bolded section below, I can’t seem to get past the “Cast off 3(4,4) sts , K3(4,4) inc the 1 st rem.on the needle, turn”. I cast off the 4 stiches, then knit 4, and then turn the whole piece? but then purling the next row would be just those few stiches?

Would appreciate any help!

**Using 10mm needles, cast on 48 (54, 58) sts
Work 10 rows in k2,P2 rib
Next row: Beg with a k row, and changing to 12mm needles, work 34(36,38)cm or desired length to armhole) in st.st, ending on a P row
Next row: Cast off 3 sts at beg of next 2 rows
Next row: K2, S1, K1, PSSO, K to last 4 sts, K2tog, K2
Next row: P2, P2tog, P to end, P2 tog tbl , P2
Now cont. dec.as set until 30 (34,38) sts rem **
Continue straight until armhole measures 22 (23,24) cm with R.S facing for next row
Shoulder Shaping
Cast off 3(4,4) sts , K3(4,4) inc the 1 st rem.on the needle, turn,
P 1 row
Cast off rem 3(4,4) sts
Now leave centre 18(18,20) sts onto a st holder
Rejoin yarn to rem sts, K to end
Next row: Cast off 3(4,4) sts purlwise, P to end
K1 row
Cast off rem 3(4,4)st

Welcome to KH!
Yes, turn and purl the row across 4sts then turn and cast off the remaining 4sts. You’ll get to the center sts and the other shoulder directions in the next steps.