I took the index with the words, converted the quantity to binary, included a few zeros, calculated the sha256 digest, took the 1st Section of the hexadecimal to transform it to binary, additional 3 zeros to your 8 digits on the binary and obtained 00000010011 which interprets to 19 in https://prbookmarkingwebsites.com/story21867520/the-fact-about-bip39-seed-phrase-word-list-that-no-one-is-suggesting