I took the index of your words, transformed the selection to binary, extra a few zeros, calculated the sha256 digest, took the first Portion of the hexadecimal to transform it to binary, additional 3 zeros for the 8 digits on the binary and got 00000010011 which translates to 19 in https://yesbookmarks.com/story18919608/ledger-seed-phrase-bip39-no-further-a-mystery