Sorry I meant SM-18 (released in 2019, hence the confusion). But for completeness the only information available on SM-17 is one of two incredibly long articles written by Piotr Wozniak[1,2]. SM-18 is only a minor improvement over SM-17, with some changes to how difficulty is calculated[3].

[1]: https://supermemo.guru/wiki/Algorithm_SM-17 [2]: https://www.supermemo.com/en/articles/history [3]: https://supermemo.guru/wiki/Item_difficulty_in_Algorithm_SM-...