I tested the lead number field to see how it works. The system will accept any arrangement of numbers, as long as there is a dash in the middle. So the system seemed OK with anything from 2-2 to 5555-55555. The system will tell you if the format is unacceptable.
Hopefully the lead number is something that is just "nice to know" for Hilton, and it won't delay the processing of a complaint.