For words that have only 3 letters, there isn't any 4th letter. One example is with the word “include”, there isn't any much more letters Later on and therefore needs to be the word "increase". The word “addict” is inside the BIP39 wordlist however , you might have employed “addi” https://artybookmarks.com/story18870356/how-much-you-need-to-expect-you-ll-pay-for-a-good-valid-bip39-seed-phrase