Draw a circle while staying as close to the template as possible. When you're done, release your mouse. It will show a graph of the distance from the actual circle over the time you drew it. (lower is better) If it says "Not a circle", you made the circle too quickly or you didn't close it all the way.
I thougt it was realy hard to create a perfect circle in this game so i added help. Yes, the thumbnail is supposed to look like a YouTube clickbat thumbnail.