Finance Question

Finance question, since I took zero econ classes in college. This episode of the West Wing, they’re talking about the ramifications of a certain announcement, and they talk about the effect it will have on the markets. One advisor says there will be more sellers than buyers, implying that markets will go down.

Someone needs to explain that statement to me. If I’m not mistaken, every market transaction necessarily requires both a seller and a buyer, you can’t have one without the other. So regardless of whether markets are up or down, the number of sellers and buyers should always be exactly equal, right? Or does it mean there are more people wanting to sell than buy? How to you exactly measure that? Or does it mean something else I don’t understand?