The first thing to understand is that the thermostat operates to control the temperature of the room.It will switch the heater on and off to maintain a constant room temperature.
Turning the thermostat to a high number does not increase the heat coming out of the heater. The output is constant at two kilowatts, but it will result in the heater running for a longer period, thus giving a higher temperature in the room.
How to set the thermostat.
(A) Switch on the fire.
(B) Turn the thermostat to number 10.
(C) When the room is at a level of warmth that you require, then turn the control knob back very slowly until you hear a click, and the heater stops.
(D) Leave the thermostat at that number. The heater will then switch on & off to maintain the temperature you selected. Please note that number 10 will not give more heat than number 2.