I took the index from the words, converted the variety to binary, included 3 zeros, calculated the sha256 digest, took the first Portion of the hexadecimal to convert it to binary, additional 3 zeros to your eight digits with the binary and obtained 00000010011 which interprets to 19 in decimal. https://letsbookmarkit.com/story18764135/considerations-to-know-about-bip39-seed-phrase-generator