What does it mean that the coordinator overhead?

Coordination itself costs effort — keep the coordination cost proportional to the benefit.

Example: You are managing a project with three people. Communication is fluid — three bilateral channels, quick sync meetings, fast decisions. Then the project falls behind and someone suggests adding four more people. Now you have seven people and twenty-one communication channels. Meetings that took fifteen minutes take an hour. Every decision requires bringing more people up to speed. Status updates multiply. The new people need onboarding, which pulls the original three off productive work. Two weeks after 'adding resources,' you are further behind than before — not because the new people are incompetent, but because the coordination overhead of seven people exceeds the productive capacity those extra people added. The project did not need more hands. It needed the same hands with less friction between them.

Try this: Identify a project, team, or recurring collaboration in your life where more than three people are involved. Map every coordination mechanism currently in use: meetings, status updates, shared documents, chat channels, email threads, approval workflows. For each one, estimate the total person-hours per week it consumes across all participants. Sum the total. Now ask: what percentage of the group's total available hours goes to coordination versus production? If it exceeds 30%, pick the single highest-cost coordination mechanism and design a way to eliminate or halve it — by reducing participants, frequency, or scope. Run the change for one week and measure whether productive output increased.