royal mail -- How to edit the rate ?

Hi guys,

Always got a problem when i come here.
I met a problem on the royal mail rate setting, it seem to be a built-in rate in OC, since whatever i set the type of royal mail. i can not find the place to edit or add the rate.

i am using v1.5.0 and v1.5.1

hope to hear from you soon.

catalog/controller/shipping/royal_mail.php

In OC 1.5.1.3 you can edit in admin