There is a lot more to the process unfortunately, especially when it is done for commercial purposes. Guinness has a special section on their website just for this: https://www.guinnessworldrecords.com/business-marketing-solutions
Additionally to verify the record, you need to pay for a Guinness Judge or Adjudicator to come to your location (flights, hotel stay, local transport). There is a per year fee to be able to use the Guinness name. It all adds up.
You can read more information here: https://en.wikipedia.org/wiki/Guinness_World_Records#Change_in_business_model
Quote: “While any person can theoretically send in a record to be verified for free, the approval process is slow. Would-be record breakers that paid fees ranging from US$12,000 to US$500,000 would be given advisors, adjudicators, help in finding good records to break as well as suggestions for how to do it, prompt service, and so on.”