I took the index with the words, converted the range to binary, extra 3 zeros, calculated the sha256 digest, took the first part of the hexadecimal to transform it to binary, additional 3 zeros into the 8 digits on the binary and got 00000010011 which interprets to 19 in decimal. https://bookmarkbooth.com/story19494337/the-fact-about-valid-bip39-seed-phrase-that-no-one-is-suggesting