I took the index with the words, transformed the variety to binary, extra 3 zeros, calculated the sha256 digest, took the main part of the hexadecimal to transform it to binary, included 3 zeros to your eight digits with the binary and acquired 00000010011 which translates to 19 in decimal. https://bookmarkusers.com/story18633087/5-simple-techniques-for-bip39-word-list-pdf