Hi sgt,
I explained this in the article above under function who counts the images states:
In our sample we have a total of 20,000 images in backlog but 15,000 are IN_PROCESS, 2,000 in NOT_MANAGED state and 3000 NOT_STARTED, each of this states demands different actions but just to start it will be good to know why those 2000 images are in NOT_MANAGED state, by personal experience are either bad images or backup policies not using SLP’s, if you have many 800 errors is highly a list of bad images.
Hope this helps.
This is my personal opinion and not of the company I work for.