KoKo Credits is different from Challenge Points
Challenge Points are cumulative, where it is a reward system that affects the level of your ranking in leaderboards.
Any challenge points obtained are directly added to your overall points, and this affects your ranking position in various leaderboards e.g. Hero of the Day, Top Brain etc.
KoKo Credits are consumable, where it is a reward system that helps to improve your learning experience.
KoKo Credits earned can be spent on unlocking premium features, such as StoryMath chapters, which will help learning maths through comics.