I took the index in the words, transformed the number to binary, added three zeros, calculated the sha256 digest, took the very first Portion of the hexadecimal to transform it to binary, included three zeros to the 8 digits of the binary and got 00000010011 which interprets to 19 in https://bookmarkingdepot.com/story19540597/not-known-factual-statements-about-bip39-explained