You can just edit the customer statistics if you'd like to change the numbers. You can also import them from Excel.
Use GridView to build the Excel spreadsheet necessary by calculating the figures you want from your OrderEntry history. The formula will be something like:
IF(AND({Invoice date} >= {BeginDate},{Invoice date} <= {EndDate}),{Amount},0)
for each column in the statistics you want to correct. Make {BeginDate} and {EndDate} calculate columns containing the ranges of dates you want included in the numbers.
The Toolkit for Adagio's next release has an option that will recalculate these numbers from the historical figures in Adagio Receivables. This might be an easier approach.