I took the index on the words, transformed the amount to binary, included three zeros, calculated the sha256 digest, took the main part of the hexadecimal to transform it to binary, additional a few zeros to the 8 digits of your binary and received 00000010011 which interprets to 19 in https://bookmarkblast.com/story19032618/not-known-factual-statements-about-bip39-explained