I took the index in the words, converted the range to binary, extra three zeros, calculated the sha256 digest, took the first A part of the hexadecimal to transform it to binary, included a few zeros to your eight digits on the binary and received 00000010011 which interprets to 19 https://yxzbookmarks.com/story19008512/helping-the-others-realize-the-advantages-of-bip39-mnemonic-phrase-tool