It starts with #KEF and then followed by numbers f.e. #KEF0000. You will only need the 4 numbers f.e. 0000.
The module only accepts numbers not letters. Please enter the numbers from your booking confirmation. It starts like this: #KEF followed by numbers. Still in doubt please continue reading:
If you made a quote or sent yourself an e-mail before actually booking your number might start with the letter Q or U. This is not the right number. Please look for the number that starts with #KEF.