premise: Lamme Goedzak is a character in Charles De Coster's novel "The Legend of Thyl Ulenspiegel and Lamme Goedzak" (1867). He is the best friend of Thyl Ulenspiegel. While Ulenspiegel himself is derived from Dutch-German-Flemish folklore Lamme Goedzak is entirely created by De Coster. Despite this he has become one of the most recognizable Flemish folklore characters since.
hypothesis: Charles De Coster published a novel in 1865
reason: The context says that De Coster published the novel in 1867. It does not say if it was his first novel ever or whether he published any novels before that, so it's possible he also published a novel in 1865 but we have no way of knowing based on the context alone. The system was likely confused by the dates.