It's written that "You can also change the client seed if you wish." but I still haven't found how to do it.
In the HTML code the field has a read-only attribute but even if you remove it, the client seed entered isn't taken into account.
https://i.imgur.com/h8Gi2tm.jpg
You can remove the client seed from there and manually input it as you want.
Server seed hash automatically changes after every roll, client seed changes every time while you visit/refresh the page. I'm also unable to change the client seed at wheel of fortune provably fair page.
Edit: Sorry, I just tried but it didn't work in this way. TheQuin should clarify about the matter.
It's the JavaScript that generates the random client seed rather than the HTML. We'll update it so it's easier to manually change it.