I have a patch that I make that with personalized names. I have a 10 character limit.
The customer is able to enter more than 10 charters even with this limit. Etsy has a glitch.
If it is your Custom Name Patch, Etsy issues a warning when a customer goes over nine characters. I see, in red, "You've reached the limit! Use nine characters or less." The letters I entered are also underlined in red (probably because I used all x's).