This basket weave pattern is a multiple of eight stitches, both horizontally and vertically. Any increases or decreases in this pattern (to make, say, an afghan or a purse) should be made in multiples of eight stitches.
To determine the required number of stitches for your project, do a 16 x 16 stitch swatch in pattern, then measure eight stitches, horizontally and vertically. Divide the desired width and length by these values by 8 to determine the number of multiples of eight required, then add the measurements of the outer stitches that make up the eyelet border.
Each side of the border takes up 6 stitches, or a total of 12 stitches. So, get your multiple of 8 that you need for your dimensions then add twelve stitches. Or, if you want to be closer to your exact dimensions, subtract one multiple of 8 and let the border count for one multiple.