This graph is called Sales vs Receivables if Sage Simply Accounting is set to use accounting terminology.
Sales vs Sales Due is a bar graph showing sales and unpaid sales for all or selected accounts for each month in the current or previous fiscal year.
Use it to compare the total sales for the month against the amounts your customers owe you.
Print the Sales vs Sales Due graph at month end and at the end of your fiscal year for auditing purposes and at other times as required.