I took the index of your words, transformed the quantity to binary, additional three zeros, calculated the sha256 digest, took the initial Section of the hexadecimal to convert it to binary, additional 3 zeros on the 8 digits in the binary and received 00000010011 which translates to 19 in decimal. https://bookmarklinking.com/story5064510/ledger-seed-phrase-bip39-no-further-a-mystery