Bip39 Checksum. At the start you ought to store it SEPARATELY out of your seed. Getting your seed and also your passphrase in the identical spot defeats the purpose of having a passphrase in the first place. At its core, a BIP39 passphrase modifies the cryptographic strategy of wallet generation. https://social40.com/story4182358/bip39-list-https-linktr-ee-bip39-the-basic-principles-of-bip39-mnemonic