I took the index in the words, converted the amount to binary, additional a few zeros, calculated the sha256 digest, took the first part of the hexadecimal to transform it to binary, included three zeros for the 8 digits from the binary and got 00000010011 which interprets to 19 in https://geniusbookmarks.com/story18821091/bip39-seed-phrase-mnemonics-generator-an-overview