The temperature inside the egg tubs is going to vary depending on each clutch. Typically, an egg tub with a clutch that is close to hatching will have a higher temperature compared to a clutch that is not.
When incubating ball python eggs, I set my thermostat at 89.5°F, and I only measure the temperature of the ambient air, not the inside of the egg tubs. I use a digital thermometer inside the incubator to verify the ambient temperature and to make sure the thermostat is working properly.
I have a small CPU style fan inside the incubator as well.