Look at the numbers. It has nothing to do with the speed of eating. If you have 6 courses of food and 7 settings of silverware, then there is one more set of silverware then you need. After you eat 6 courses, there will still be silverware left on the table. A fork just sitting there.
(In a formal dinner, the silverware is arranged on the outside of the plate area. You use the silverware on the outside for each course and that silverware is collected with the dishes when the course is done. Then you use the next set of silverware on the outside for the next course, etc.)