A useful dashboard answers a few connected questions from one agreed dataset. For this small shop, the manager needs revenue, performance against target, and the monthly direction. Keep the period and units consistent across those views. A six-month total beside a one-month target would mislead even if both numbers were individually correct.
Calculate headline values from the same source rows used by the chart. Use a ratio of totals for overall target attainment, rather than averaging monthly percentages when targets differ. A QUERY summary can make the chart's source visible and easy to inspect.
The dashboard exercises focus on the calculations and chart setup. Don't type a finished total or hide an error behind decoration. A zero month is valid; a missing month needs investigation. The source remains in the workbook so the next analyst can follow the headline back to its rows.