It is massive, lots of papers analyzed, but just the Abstract part of each.
One way you could look at it is: some authors used an LLM to create the abstract from the paper contents. "Hey, there's a lot of new books with AI covers"
One other way is: There could be a correlation between LLM usage in the abstract and LLM usage during the production or writing of the paper. "Hey, I wonder if this book with an AI cover also was written by an AI. It should be investigated"