Polymerized Oil or Burned Oil?
There is no clear cut border between polymerized and burnt, it is a continuum. The center went clearly farther than the sides, which is common enough in stovetop seasoning. 

If the coating in the middle of the pan doesn't work well for you, you can strip and reseason to a lighter state, preferably in an oven. If food cooks well on it, you can keep it as it is.