Compare shapes, not just peaks
Look for clusters of stronger hours. A cluster is usually more informative than one unusually high cell.
The heatmap scales each day independently, so use the printed raw values when comparing one day with another.
Keep the unit consistent
Customers per hour and relative indices describe different things. Pick the unit that matches your notes and do not switch units halfway through a week.
Observe again before generalizing
A single week can contain unusual events. Save your conclusion outside the site, gather another complete week, and compare the pattern again.