Woocommerce advanced export pro

Hello,
we are using the plugin
ADVANCED ORDER EXPORT FOR WOOCOMMERCE and it is great.
We have to create a TXT file for our shipping company and they ask to create a text file with position fixed fields.
Example:
Name 10 character, surname 12 characters,postal code 5 characters

TXT FILE
Name*****Surname*****20900
So we need to fix the field lenght, is there a way to do so, maybe with custom php code? I see that is possibile to use custom php under “misc settings” but i don’t know what can I write in that field.

Thank you