It means that the Certificate of Incorporation and Preferred Stock Serties Resolution may contain clauses or suchlike that allow for external facts to be used. They would have to describe what types of external things may be usaed, but not the facts themselves. I imagine that they might, with voting rights, have something that allows them to make decisions that could affect future voting rights without specifying what but how this would be done, so that they are future-proofing themselves.