The original title of Machiavelli's Discorsi was Discorsi sopra la prima deca di Tito Livio, literally (according to Wikipedia) "Discourses on the First Decade of Titus Livy". "Decade" here refers to the first ten books of Livy's Ab urbe condita. However, the tenth book ends with the end of the war against the Samnites in 292 BC., while the Discorsi also discuss events and topics from later books. So why does the title specifically mention the first ten books?