Day-part mix tells you the business model
Breakfast, lunch, and dinner are different businesses. Most successful diners get 50–70% of revenue from breakfast and lunch combined, with dinner as supplemental. The breakfast trade tends to be regulars; lunch attracts a mix of regulars and convenience traffic; dinner competes with every other restaurant in town. Verify the revenue breakdown by day-part and the trend over time. A diner heavily dependent on dinner is a harder business than one with strong breakfast and lunch.