I mean if the control strategy sheet was right it says once it has reached setpoint of 20C it will continue to heat to 24C ramping down a step every 1C.

In high ceiling mode the unit does not do this, once it has reached 20C it will continue at 100% tilll reached 24C. Are you sayign that if high ceiling mode is activated after it has reached 24C it will then start to ramp down and if another 4C increase is sensed it will stop?

How complicated that sheet is!