I took the index on the words, converted the selection to binary, included a few zeros, calculated the sha256 digest, took the first Component of the hexadecimal to transform it to binary, extra three zeros into the 8 digits in the binary and obtained 00000010011 which interprets to 19 in https://ticketsbookmarks.com/story18748652/the-fact-about-valid-bip39-seed-phrase-that-no-one-is-suggesting