MK138 thermostat range modification, low end to zero degrees

I bought MK138 thermostat kit and put it together. It works as it should.

So: temp range is friom +5 to 30 degrees celsius, could it be modified to get from 0 to 30 degrees? I have aircon device bottom plate water drain holes freezing at winter and I have warm up cable installed to keep it from freezing shut but I need something to control the heating so the bottom plate cable starts warming up when temperature gets to zero degrees.

I read all kind of forum posts about increasing the thermostat temp range but I have not found what I am looking for.

I guess it could be done changing resistor values but I don’t know how to measure correct resistor values. Any help or advice would be appreciated. thanks.

If you look on the board next to the pot you will see R6 with a arrow down Tmin.
I think this mean decrease the resistance of R6 for the minimum temp.