Hi There!
Thanks for getting in touch with us! Let me help you with this topic.
The ticket # is created once the attendee record is generated and is saved in the database, so there is no built in way to modify it.
Changing how the ticket # is generated would require some custom coding.
As a reference, let me point you to the following article about making tickets > https://theeventscalendar.com/knowledgebase/making-tickets/
I hope that helps! Let me know if you have other questions and I’d be happy to help.
Best,
Victor