Hi Chandan,
i)Your itab data is not modified accordingly, please refer to the highlighted statement below:
Your code:
74 wa_tab-BES,
120 sy-vline.
MODIFY ITAB FROM WA_TAB.
ENDLOOP.
ii)In your Projekt ABAP AZT fiel upload doubt4.jpg, you can see the list width column, put 9999 inside it and press enter.
Thanks.
Regards,
Keng Haw