Let's talk about clamp sizes. They are stupid. Clamp sizes are labled to match a seatpost size. A 22.2mm clamp is designed to go along with a 22.2mm seatpost.
The 22.2mm size referes to the external diameter of the seatpost. The tricky part is that a 22.2mm seatpost goes inside a unicycle frame with a 22.2mm internal diameter. The external diameter of the frame will usually be closer to 25.4mm. So the internal size of the clamp will be 25.4mm, but we call is 22.2mm because that's the post it matches.
So a 22.2mm clamp actually fits a frame with a 25.4mm external diameter.
And a 25.4mm clamp fits a frame with a 28.6mm external diameter.
Ergo a 28.6mm clamp fits a frame with a 31.8mm (32mm) external diameter.
Like I said, stupid. But that's how it works.