great question.  The only thing I can say to your question since I have been diagnosed as mixed and told my depression is moderate, that maybe that is what it means.  Mixed is suppose to be when you are having manic symptoms along with depressive ones.  I describe my mixed episodes, (I am trying to figure out what an episode is because I seem to constantly be in "episodes"), but anyway, my episodes are getting very irritable and mean to my husband, being frustrated, overwhelmed with everything, not being able to do anything because my concentration is not there, wanting to get up and do things but feeling like I am just stuck, being nice and calm one minute and turning into a Mean bitch the next....and while all this is going on, I am crying and feeling down in the dumps, thinking thoughts of wishing I were dead.  I guess that is what a mixed episode is.  Please tell me what your's is like?  I think moderate would be that you are not totally out of control...you are not psychotic, or out of your mind when manic, when depressed,  I would think it would mean that you are functioning, but on a scale of 1-3, you function at a one and a half.  Not suicidal.   raku