Probability of Matching Letters

Robert and Justy play a game: Robert forms a four-letter word where each letter comes from the set $\{A,B,C,D,E,F,G,H\}$ without repetition. Justy then guesses the word by providing another four letter-word using the same rules. Instead of winning only when Justy matches Robert's word, Justy now wins if his word and Robert's word has at least one matching letter placed in the same position. What is the probability that Justy wins? The answer is in the form $\frac{\alpha}{\beta}$ for coprime integers $\alpha$ and $\beta$. Input the answer as the sum $\alpha +\beta$.