The information on this design states that the "model" was stitched on 28-count fabric and says, in parentheses, "over 2". Is that what you are referring to? If so, it means that you would stitch your X's
Over Two squares on the fabric. If you stitched this 'over 1" square on 14-count AIDA fabric, your finished project would be almost exact same size. In stitching "over 2": if you bring your needle up in the lower left corner of a square, instead of going down in the upper right corner, you would SKIP Over that corner and go diagonally to the next upper right corner to put your needle through.
If this sounds confusing, the "scarletquince.com" website has excellent tutorials for help; also You-tube would probably have a good tutorial on counted cross stitching "over two". Hope this helps! :)
I'm not an employee of ECS, but a stitcher on this "chat" that saw your question. :)