In detail, γ considers that the three annotators agree on the fact there is a first unit on the left of the continuum, but do not fully agree on its category (A, B, and A), that two annotators only consider that there is a unit in the middle of the continuum, of category B, and that only one annotator found a third unit of category C at the end of the continuum.
γ has created three empty units, one because annotator 3 missed the second unit, and two because annotators 1 and 2 missed (compared with 3) the third unit.