I took the index with the words, converted the range to binary, added 3 zeros, calculated the sha256 digest, took the main Element of the hexadecimal to transform it to binary, additional 3 zeros to your eight digits in the binary and obtained 00000010011 which translates to 19 in decimal. https://web.archive.org/web/20241123074420/https://bip39-phrase.com/