CullAi automatically detects all people in a photoshoot and gives importance based on number of photos they are part of. Importance is used as weight while calculating overall AI score of a photo. So that rating of photo with an important person in focus will be more than that of a photo of her out of focus and instead not important person in focus.
This in turn affects auto rating and auto pick choices. You can adjust importance of individual person manually also. Consider, for example, a wedding in which the bride and groom are more important than one of the guests who may also appear often in the photos. Updating importance manually will re-calculate auto ratings and auto picks.