And possibly different litter. Even with a small box, the cat will usually get fully inside as best they can. This looks like the cat is highly averse to this litter.
If you ever want to prevent, or are having, litter box issues with your cat, check out Dr. Patricia McConnell's 'The Fastidious Feline'. It's very short, useful and goes over everything you need to know about cats and litterboxes.