I took the index with the words, converted the variety to binary, additional a few zeros, calculated the sha256 digest, took the 1st part of the hexadecimal to convert it to binary, extra 3 zeros on the eight digits of your binary and got 00000010011 which translates to 19 in https://letsbookmarkit.com/story19107434/bip39-seed-phrase-mnemonics-generator-an-overview