I took the index of the words, transformed the amount to binary, extra 3 zeros, calculated the sha256 digest, took the main Element of the hexadecimal to convert it to binary, included three zeros to your 8 digits on the binary and received 00000010011 which interprets to 19 in decimal. https://socialmediainuk.com/story20645540/the-basic-principles-of-bip39-passphrase-generator