If the highest rated participant in
an opposed roll has an ability rating above 100%,
the difference between 100 and their ability rating
is subtracted from the ability of everyone in the
contest (including themselves).
If the adventurer has a skill above 100% and that
skill is opposed by another skill lower than the
adventurer’s skill, the opposing skill is reduced by
the amount that the adventurer’s skill is above 100%.
The implication with the second description is that the higher skill is not reduced.