When Judges are assigned to Competitors (more on auto assignments here), they will be preferentially assigned to Competitors in their matching Group. 

This may be affected by your selections on the Event Dashboard page, like:

IMPORTANT: If Judges are in multiple Groups, they may be assigned Competitors from ANY of those Groups. There is no order preference of the Groups.  

If you want to restrict judge matching so that judges do not get assigned any projects outside of their Group, Wildcards must be set to -1 (negative one).