Thermometer reading differently?

well, I have no idea what I should do. Temperature under hide seems to be always higher than other part of the hot spot. Tried lowering my thermostat, reaches around 93 degrees under hide and 88~90 on other part of hot spot. Is this a good set up? Cool side seems to stay around 77 degree. Haven't insulated my big big window in my room yet and still winter so I feel like I am in the safe side. Plus I am making 5 sided melamine to put my tub in to get better heat.