Interest calculated on past due accounts seem high

SUGGESTED

Client is charging 2% interest on overdue accounts.  Sage says 422.54 in interest on the following invoices - on the 15th-day interest starts, ( not doing statements until Dec 31, so used Dec 31 as end of statement date).   I thought it was high, so calculated it in excel.  Is Sage incorrect? Or am I doing my excel formulas incorrect?

Here are the formulas I used in excel