For words that have only three letters, there's no 4th letter. For example with the word “include”, there isn't any a lot more letters afterwards and therefore has to be the word "increase". The word “addict” is in the BIP39 wordlist but you might have used “addi” for “addict”. Stability: https://single-bookmark.com/story18956163/how-much-you-need-to-expect-you-ll-pay-for-a-good-bip39-seed-phrase-mnemonics-generator