BI Publisher not sorting data correctly

 I have a RTF template which has the following sort order <?for-each:G_INVOICE?>
<?sort:SE_CLIENT_NAME?>
<?sort:SE_DIVISION?>
<?sort:SE_FILE_NUMBER?>
<?sort:TRX_DATE?>

When I review the excel output , It sorts correctly by SE_CLIENT_NAME and SE_DIVISION but it does not sort by SE_FILE_NUMBER within the SE_CLIENT_NAME and SE_DIVISION.

I also tried just sorting it by SE_FILE_NUMBER independently , still it does not work.

It shows the SE_FILE_NUMBER in the following order on the excel output

SE_FILE_NUMBER
8053341
8053151
a8026530
8047382
8052959
8052856
8050172
8050172
8052555
a8052883
8020433
8020433

If you observe , a8026530 and a8052883 should be at the bottom. Also 8052959 is coming before 8052856. It is not sorting correctly..