Something out of the ordinary happens. There are surprises. Perhaps a customer has changed directions or an area you thought you had to work in is now going to be used by another contractor. Any of these can cause momentary change to your labor count. Be prepared for the unexpected with a Plan B.
Be swift and clear about addressing the “too many employees” problem. Create a lean work team, and remember, having one less worker is often more productive than having one too many.