I took the index with the words, transformed the range to binary, extra a few zeros, calculated the sha256 digest, took the very first Portion of the hexadecimal to convert it to binary, additional 3 zeros to your 8 digits on the binary and got 00000010011 which translates to 19 https://socialmphl.com/story20748509/helping-the-others-realize-the-advantages-of-bip39-mnemonic-phrase-tool