how do i set my siemens rdj10rf?

i also have a siemens rdj10 rf and am also confused as to the difference between the comfort and setback settings,what do they mean?is it as the other person has suggested that the setback temp is the temp it reverts to in between the timed period ?any help on this would be gratefull as had some high bills and want to make sure i am setting it right .many thanks