Pls. explain the logic in Customer - Summary Aging Simp.

PL337

I need to create SQL Server reports, using the same data from the Customer - Summary Aging Simp.

So far I've successfully queried the data for 31-60 days, 61-90 days and Over 90 days.
I'm having trouble writing the query for 'Not Due' and '0-30 day'

Example:

For 31-60 days I have this SQL query with a Start Date '02/26/2012':

Select SUM([Amount])
FROM [BAY-PROD].[dbo].[MYCOMPANY_$Detailed Cust_ Ledg_ Entry]
Where [Customer No_] = '1000537'
and [Initial Entry Due Date] between
DateAdd(d,-60,'02/26/2012')
and DateAdd(d,-31,'02/26/2012')

In the query above, the sum matches the number from the '31-60 days' column in the Aging Report.

When I apply the same logic to 0-30 days, I get different results.

My query for '0-30 days' would be (for the same start date):

Select SUM([Amount])
FROM [BAY-PROD].[dbo].[MYCOMPANY_$Detailed Cust_ Ledg_ Entry]
Where [Customer No_] = '1000537'
and [Initial Entry Due Date] between
DateAdd(d,-30,'02/26/2012')
and '02/26/2012'

The results from this query differs from Aging report.

My query for 'Not due' would be:

Select SUM([Amount])
FROM [BAY-PROD].[dbo].[MYCOMPANY_$Detailed Cust_ Ledg_ Entry]
Where [Customer No_] = '1000537'
and [Initial Entry Due Date] > '02/26/2012'

Again, the query result differs from the Aging report.

Can anyone help with the calculation logic?

Thanks in advance!