For words that have only three letters, there isn't a 4th letter. Such as with the word “increase”, there are no extra letters Later on and therefore has to be the word "insert". The word “addict” is during the BIP39 wordlist however you would have utilised “addi” for “addict”. Art https://mixbookmark.com/story4571403/the-5-second-trick-for-ledger-seed-phrase-bip39