Please correct me if I've constructed this portion incorrectly, for I have not tried the blouse on my grandaughter as yet. I positioned the patch just a smidgen over the gatherings. If I was to position the patch according to the markings, the gathered lines would get matted down, looking less like tiny gathers and more like pleats. Doing this, subtracted from the opening at the neck by 1/2", but I don't think it should affect the fit.
Tip: When directions call for 2 rows of basting stitches for gathers, I sew three:
1-along the seam allowance; 2- 1/4" less; 3-1/4" more than the seam allowance. I also use a standard or smaller stitch on children's clothes when sewing gathering stitches because this makes the gathers tiny and more suited for the little ones.