When you have first installed Clever Credit you will need to run the Calc. Statistics action on the Clever Credit Setup page.
This action runs through existing invoices and payments for customers to calculate the number of days for each invoice to be paid and how many days overdue each payment was.
The average statistics are displayed on the Clever Credit page for each customer. Drilldown on the figure to see the statistic entries for each invoice and to plot a chart of the customer's payment performance over time.
Once you have clicked this you will get a notification to say this is running in the background as it could take a little time.