I took the index from the words, transformed the amount to binary, additional 3 zeros, calculated the sha256 digest, took the very first A part of the hexadecimal to convert it to binary, included 3 zeros to your 8 digits on the binary and got 00000010011 which translates to 19 https://mediajx.com/story21496262/the-fact-about-bip39-seed-phrase-word-list-that-no-one-is-suggesting