I took the index with the words, converted the range to binary, added 3 zeros, calculated the sha256 digest, took the 1st Component of the hexadecimal to transform it to binary, additional 3 zeros to your eight digits with the binary and obtained 00000010011 which interprets to 19 in decimal. https://thegreatbookmark.com/story18961562/not-known-facts-about-bip39-english-words