He may be asking about when both evaders and chargers go off table. It's clear that if the chargers move distance exceeds the sum of the evade dice roll plus separating distance then the evader is destroyed. I assume if the evaders escape then they both dice to return once they reorganise off board.
If the skirmish evade move is less than the charge distance then the skirmishers are destroyed. If the charge move takes the chargers off table then they test to return to the table as per the rules.