That's an earring that I pin at the top to keep my stitchery going in the right direction. On a piece like this it doesn't matter a whole lot since it's symmetrical. But the blue lines match the lines match the dark lines on the chart, so the earring helps keep me straight.
It's a bit of a challenge stitching 18 stitches per inch, but my magnifier is helping.
I may have cut my fabric too small, but I'll make it work in the finishing.