I took the index with the words, transformed the range to binary, included 3 zeros, calculated the sha256 digest, took the 1st Element of the hexadecimal to convert it to binary, included a few zeros into the eight digits of your binary and got 00000010011 which interprets to 19 in https://lingeriebookmark.com/story8630486/facts-about-bip39-seed-phrase-github-revealed