The way Solo Leveling and other Manhua are drawn, the panels are long but the story is short. Hence, there is much less what a Manhua covers in one chapter than a Manga. God of High School's anime covered about 80-90 chapters of manhua within 10 episodes of the anime. Hence, for Solo Leveling to receive an Anime adaptation, the manhua must at least have close to 150-189 chapters.