I took the index of your words, transformed the range to binary, included three zeros, calculated the sha256 digest, took the initial part of the hexadecimal to convert it to binary, added a few zeros to the eight digits from the binary and got 00000010011 which interprets to 19 in https://sociallytraffic.com/story3709666/new-step-by-step-map-for-bip39-english-words