I’m going to chain 27 and have 26 stitches. I did 27 rows. My square measures 6.5 inches wide by 6.25 inches tall.

I used some contrasting yarn to lightly baste (is that the right word?) around the area in the center that is the size of the chart 15 x 15. I can yank that out later. I have 6 extra rows above and below and 5 extra stitches on each side of my box.