I took the index on the words, transformed the number to binary, added a few zeros, calculated the sha256 digest, took the initial Element of the hexadecimal to transform it to binary, included three zeros to your eight digits of your binary and got 00000010011 which translates to 19 in https://nanobookmarking.com/story18945993/considerations-to-know-about-bip39-seed-phrase-generator