Attack – Is the choice of scale effects per role or per conflict limited?

System Toolkit page 67 provides the scale mechanism for attacks and defenses between enemies, groups, etc. of different sizes. However, I am not sure how to interpret the inner "or" (ie the "that" or "within the two effects).

Especially if it means applying a bonus to the attack or Defense, this means that only one of the two can be used within the same role (since one of the attackers and the other is a defender), or that means that the side that benefits from +2 damage should do so Not get the damage reduction in the the same conflict? (The same question applies to the attack / defense skill bonus.)