I took the index in the words, transformed the number to binary, added three zeros, calculated the sha256 digest, took the primary part of the hexadecimal to convert it to binary, included three zeros on the eight digits of the binary and received 00000010011 which translates to 19 in decimal. https://bookmark-group.com/story4420938/considerations-to-know-about-bip39-seed-phrase-generator