Rule 437.5.a

Damage can be assigned to a Unit up to a value that would be Lethal considering the Prevent Value of all Prevent Actions on a Unit, following the normal rules for damage assignment. Example: A unit with 2 [M] is being assigned damage in the combat damage step. The unit has “prevent the first 3 damage I would take each combat.” The unit would need to be assigned 5 damage in order to have lethal damage assigned to it.