I took the index on the words, transformed the number to binary, additional three zeros, calculated the sha256 digest, took the 1st A part of the hexadecimal to transform it to binary, additional 3 zeros on the 8 digits in the binary and acquired 00000010011 which interprets to 19 in https://bookmarkcitizen.com/story18826495/5-simple-techniques-for-bip39-word-list-pdf