Creditor Reference is an alphanumeric string, up to 25 characters long, with the letters "RF" at the beginning. After the letters are two check digits, which confirm that the reference will be entered correctly.
:~/pyrfgen$ python3
Python 3.7.3 (default, Jul 25 2020, 13:03:44)
[GCC 8.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from generator import *
>>> print(generateRfReference("Lorem Ipsum"))
RF34LOREMIPSUM