A unit does not receive combat result points for extra ranks and cannot be(see ) as long as it is disrupted.
A unit is disrupted if an enemy is attacking it in the flank or rear, and that enemy unit has10 or more. Smaller units are assumed to have insufficient mass to cause disruption.
Sometimes, an enemy unit will begin the round of close combat with enough Unit Strength to cause disruption, but takes enough casualties so that it has below Unit Strength 10. In this case, it can no longer disrupt the unit it is fighting and the extra ranks are counted as normal.