I took the index with the words, converted the range to binary, added 3 zeros, calculated the sha256 digest, took the main Portion of the hexadecimal to convert it to binary, included a few zeros towards the eight digits of your binary and received 00000010011 which translates to 19 in https://ok-social.com/story4975941/the-fact-about-valid-bip39-seed-phrase-that-no-one-is-suggesting