I took the index of your words, converted the range to binary, included three zeros, calculated the sha256 digest, took the 1st part of the hexadecimal to convert it to binary, included three zeros to your eight digits of the binary and acquired 00000010011 which interprets to 19 in decimal. https://userbookmark.com/story19431527/little-known-facts-about-bip39-seed-phrase-list