I took the index on the words, transformed the variety to binary, added a few zeros, calculated the sha256 digest, took the 1st Element of the hexadecimal to transform it to binary, extra 3 zeros towards the 8 digits with the binary and received 00000010011 which translates to 19 in https://bookmarkyourpage.com/story4186106/how-much-you-need-to-expect-you-ll-pay-for-a-good-bip39-seed-phrase-mnemonics-generator