Choke thermostat problem

After sleeping on it a couple nights: maybe there is an index mark, but it is so far away from where it should be that it can't be seen through the window. If that can be checked without loosening the adjuster nut, great. If it can't, I would not loosen the adjuster nut until there is no other option but to try making an adjustment (that is: after the carburetor is elevated to the correct height).