I took the index on the words, transformed the range to binary, included a few zeros, calculated the sha256 digest, took the 1st Element of the hexadecimal to convert it to binary, added 3 zeros towards the eight digits on the binary and obtained 00000010011 which interprets to 19 in https://yesbookmarks.com/story18953394/the-basic-principles-of-bip39-passphrase-generator