Well, 'only one suspension of reality in science fiction' might imply that within the realm of science - fiction, the author or creator limits the number of things that go against real - world physics or common sense to just one. Say, in a story about a planet with different gravity, that's the sole suspension. It allows the story to be both imaginative and still somewhat relatable as it doesn't over - complicate with too many unrealistic elements.
It could mean that in science fiction, there is typically just one major departure from the known rules of reality. For example, in a story about time travel, time travel itself is that one suspension. It's the element that defies what we know about the normal flow of time in our real world.
In science fiction, 'only one suspension of reality' can be seen as a creative constraint. By having just one, it forces the writer to focus on that particular aspect. For instance, if the suspension is the existence of telepathy in a society. The story can then explore all the implications of that one departure from reality. It could show how society is organized around this new ability, how relationships are affected, and how the overall culture evolves. This single suspension becomes the central pivot around which the entire fictional world rotates, making the story more coherent and easier for the reader to engage with as they don't have to keep track of multiple unrealistic concepts.