Illisia, the article suggests that the show has done a better job at explaining why the 20 rings. The order of their making therefor matters, with the elf rings being first, etc. But it deviates so far from the original work -- it doesn't really explain anything because the story was fundamentally altered. If you want to know why Tolkien chose 20 go to his work for the answer. I would argue the show is so far afield of the actual story it's less an adaptation than a complete reimagining.