I took the index with the words, transformed the number to binary, additional 3 zeros, calculated the sha256 digest, took the first part of the hexadecimal to convert it to binary, included a few zeros for the eight digits in the binary and got 00000010011 which interprets to 19 in https://mixbookmark.com/story4325595/an-unbiased-view-of-bip39-seed-phrase-github