I took the index in the words, transformed the selection to binary, included a few zeros, calculated the sha256 digest, took the primary Component of the hexadecimal to transform it to binary, extra 3 zeros on the 8 digits of your binary and received 00000010011 which translates to 19 in https://tetrabookmarks.com/story18846229/an-unbiased-view-of-bip39-seed-phrase-github