Suppose that two teams are playing a series of games, each of which is independently won by team A with probability $p$ and by team B with probability $1-p$. The winner of the series is the first team to win $i$ games. 

If $i=5$, find the probability that a total of $8$ games are played. 
I got this solution for this one: $7 \choose 4$$p^5(1-p)^3$+ $7 \choose 4$ $p^3(1-p)^5$

But when $i=4$ and I have to find the probability that a total of $7$ games are played, I tried solving using the same method for the previous question, but it wasn't correct. The correct solution is supposed to be $6 \choose3$$p^3(1-p)^3$.

I don't understand why they are different,, can anyone clarify?

Thanks