I took the index on the words, converted the variety to binary, included 3 zeros, calculated the sha256 digest, took the main A part of the hexadecimal to transform it to binary, included 3 zeros to your 8 digits on the binary and obtained 00000010011 which translates to 19 in https://hyperbookmarks.com/story19024673/the-greatest-guide-to-seed-phrase-bip39