Thermostat control

I'm trying to adjust a new thermostat I installed in my soda machine, but have a question about  the adjustment screw. My thermo appear to have 2 separate controls.  One of the adjustment is on the outside of the thermo and has like a pointer on it.  The other is an adjustment screw that is located inside of a small hole on the thermo.

It appears the screw inside the small hole raises and lowers the temperature, but I can't quite figure out what the adjuster is for located on the outside of the thermo housing.

Is it a micro adjustment for the temperature or is it a on-off cycle adjustment??

Thanks for any help you can give me as I new to this type of maintenance.