I took the index on the words, transformed the variety to binary, added a few zeros, calculated the sha256 digest, took the initial Element of the hexadecimal to convert it to binary, extra three zeros on the eight digits from the binary and received 00000010011 which translates to 19 in https://tinybookmarks.com/story19012772/ledger-seed-phrase-bip39-no-further-a-mystery