Business drivers: what is the "Bridge due to inconsistent rules"?

When looking at the Workforce need variation per driver chart in the Business needs tab of the SWP report, you might notice this "Bridge due to inconsistent rules" among the differents drivers impacts on the needs.

This bridge is actually here to compensate the fact that the combination of different rules leads to negative impacts that are impossible.

Example:

A team is currently composed of 10 people. 2 drivers impact this team and each one of them require a reduction of 7 people. If we apply both impacts, at the end we should have -4 persons in this team. As we are talking about people, we cannot have a number of people smaller than 0.