That tight of a coil will play hell with the life of that cord.
The absolute best way to wrap up any cord is called the "over under" method. Every single cord and hose I have gets wrapped this way including my shore line. It relieves stress on it as the turns in effect go both ways. But the biggest advantage is it will never knot up. I can take my 100 foot, 10ga extension cord, drop the coil on the ground, grab the proper end, walk away and pull the entire cord out without a single tangle or knot
This video shows the technique. Its on a video cable, but it works the same. Theres a bit of talking, the good stuff starts at about 1:25