i guess the issue is that your source field AUGDT is having NULL value.
The not initial check can't identify null entries, you need to check that explicitly. The code u should write is:
IF SOURCE_FIELDS-AUGDT IS NOT INITIAL or SOURCE_FIELDS-AUGDT IS NOT null.
RESULT = 'C'.
ELSE.
RESULT = ''.
endif.
Regards,
Anupama