though this may be a dumb question how many stitches would I subtract to make the wrap about 4 inches more narrow :shrug: :psst:
I think you can keep working on the increase rows until it's as wide as you want, then work the straight rows.
And when measuring the piece to determine the width, lay it flat with the knit side up and measure along the right hand edge from the cast on to your needle tip. Every stitch to the right of the cast on that will be dropped will add a little more width too, so take that into account. Each stitch will add maybe 1/2" or more, depending on your gauge.
Igrid is right (as usual :D)
I just stopped the increases when it got too wide, and I'm glad I did! It's huge.
There are instructions at the bottom of the pattern that will give you details. It's really simple.