What do diet ratios like 40/30/30 mean?

Carb/Pro/fat. 40-% of calories from carbohydrates 30% of calories protein 30% of calories from fat.
Diet composition. "40:30:30" is the ratio of calories obtained daily from carbohydrates, proteins, and fats, respectively popularized by the “zone diet” which is advertised widely. Most people who eat a balanced diet and burn more calories than they consume will lose weight.