I took the index in the words, transformed the number to binary, included three zeros, calculated the sha256 digest, took the initial part of the hexadecimal to convert it to binary, added three zeros for the 8 digits with the binary and obtained 00000010011 which translates to 19 in decimal. https://bookmarksknot.com/story20491465/the-basic-principles-of-bip39-passphrase-generator