What does the "short: 6,500 asked" mark next to a chapter mean?

From version 1.9.24, when the AI keeps a chapter well under the length you set, even after BookyAI asked it to continue, the chapter keeps the text it wrote and its row on the book's page shows a small "short:" mark with the length you asked for, for example "short: 6,500 asked". Hover the mark to see how many words were asked and how many the AI wrote. Nothing is lost and the chapter can be used as it is. The mark goes away by itself once the chapter reaches most of its length, for example after you regenerate it.