+1 combat result for each extra complete rank of models, to a maximum of +3.

If your unit's formation is in a complete rank, you can claim a bonus of +1 combat result for each extra complete rank behind the fighting rank, at the end of the fight, up to a maximum of +3. Note that this bonus can also be claimed for an incomplete rear rank, as long as there are enough models in it. This number of models is specified in the troop types chapter.

This is cumulative with several units engaged in the same close combat, calculating ranks for each unit, as long as they are engaged in different arcs of the enemy unit (up to a maximum of +3 per arc). If two units engage an enemy unit in the same arc, count only the highest number of ranks from one of the units.