I took the index on the words, converted the amount to binary, added 3 zeros, calculated the sha256 digest, took the 1st part of the hexadecimal to convert it to binary, included a few zeros to your eight digits on the binary and acquired 00000010011 which translates to 19 in https://topsocialplan.com/story4334575/facts-about-bip39-seed-phrase-github-revealed