I took the index with the words, transformed the number to binary, added three zeros, calculated the sha256 digest, took the very first Portion of the hexadecimal to transform it to binary, additional three zeros for the 8 digits of the binary and got 00000010011 which translates to 19 in https://socialinplace.com/story4256751/an-unbiased-view-of-bip39-seed-phrase-github