I took the index with the words, transformed the quantity to binary, extra a few zeros, calculated the sha256 digest, took the primary Component of the hexadecimal to convert it to binary, added three zeros for the eight digits from the binary and got 00000010011 which interprets to 19 in https://bookmarkinglive.com/story19592269/ledger-seed-phrase-bip39-no-further-a-mystery