Replace a White Rogers thermostat with a Lennox 51M34 on a 80MGF furnace?

My White Rogers thermostat does not always cut off when the set AC temperature is reached. The temperature drops until it reaches the setting but no further. If you tog up the setting the thermostat cuts off. If the AC is off and you tog the setting down below the current temperature, the AC turns on. When on, temperatures increase or decrease to the setting but may or may not turn off. The temperature readings are high. I would like to replace the White Rogers thermostat with a new Lennox 51M34 which I have. However There are more terminal settings on the Lennox.