VM137 Thermostat module

I have a VM137 which I installed some time ago and it’s working fine, but it could have done with a bit narrower hysteresis. I notice on the PCB that resistor R7 is marked as determining the hysteresis range, and wondered if it could substituted for a different value to achieve this?
Can you advise?
Many thanks.

The hysteresis is already at minimum for this simple circuit (R7: 6M8)
You could increase it to 10M, but the circuit could become unstable. Please experiment.