How do you adjust electric baseboard heat thermostat?

This thermostat has "Comfort Zone" witten on the front with numerals embossed in the cover where room temperature is set. When I pull off the outside cover, there are 2 small screws that look like fine adjustment inside. The thermostat varies the temperature by 10 degrees. If you set it half way right the temp will run from 66-76 degrees. If these 2 screws are like "limit adjustments" where would one start to get this temperature to vary less. This is a double pole thermostat rated at 22amps, running 2 1500 watt baseboards. 220 volt.
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