For words that only have three letters, there is not any 4th letter. For instance with the word “increase”, there won't be any much more letters afterwards and therefore have to be the word "insert". The word “addict” is in the BIP39 wordlist however you might have utilised “addi” for https://growthbookmarks.com/story19085054/how-much-you-need-to-expect-you-ll-pay-for-a-good-bip39-definition