Bad calculations are caused by missing or misentered odometer readings in the fuel, service and trip databases. Check for the following problems using the "odometer" pick list selections in each of the three list screens:
1) Make sure all odometer entries are valid, and in increasing value by date. An entry with an extra or missing digit will yield really big total miles calculations.
2) Make sure all trip entries appear with a distance entry in parentheses. When missing, the end miles are probably set to a value less than the start miles, which will overflow the calculations and show large or negative trip miles in the summary.
3) If you find a problem, narrow the date range in the report until the values are normal and increase it to find the date of the bad entry.
4) Check all vehicles for problems above, as totals default to being sums across all vehicles.
5) Try version 1.33 or higher (check beta page), which marks trip entries in the list with negative trip distance or distance greater than 10000 with "!!!!!"