Boogie Vest by Amy King

Boogie Vest

March 2004
Bulky (7 wpi) ?
13 stitches and 18 rows = 4 inches
in stockinette stitch
US 10 - 6.0 mm
US 10 - 6.0 mm
444 - 740 yards (406 - 677 m)
This pattern is available for free.

In the pattern at the “shape neck” it says:
K 1719, 23, 27, Cable Patt 9. Join a new ball of yarn and complete row with second ball. Cont. in pattern, making sure to keep your 2 sides separated by knitting the Left Front with the first ball of yarn and the Right Front with the second.

It should read:
K 1719, 23, 27work 9 sts in the cable pattern, Stop with that yarn and work up that half of the front. Attach a new ball to the other side and work the other side. Or work at the same time, keeping the split. In this way you’ll be assured that you are working the same number of rows up both sides.

You are making a split neck. Not a V-neck just a split neck.