Bip39 Passphrase Generator. The seed phrase might be converted to your amount and that is used because the seed integer into a deterministic wallet that generates many of the important pairs used in the wallet. For words that only have three letters, there's no 4th letter. By way of example https://real-directory.com/listings13148201/bip39-mnemonic-generator-https-linktr-ee-bip39-not-known-details-about-bip39-passphrase-generator