I took the index from the words, converted the selection to binary, additional three zeros, calculated the sha256 digest, took the 1st A part of the hexadecimal to transform it to binary, additional a few zeros for the eight digits from the binary and obtained 00000010011 which interprets to 19 https://totalbookmarking.com/story19063124/bip39-seed-phrase-mnemonics-generator-an-overview