I took the index with the words, transformed the variety to binary, additional three zeros, calculated the sha256 digest, took the initial part of the hexadecimal to convert it to binary, included a few zeros on the eight digits with the binary and got 00000010011 which translates to 19 in https://socialwoot.com/story20460314/an-unbiased-view-of-bip39-seed-phrase-github