Joint distribution of a random variable with its maximum

Suppose we have two independent random variables $U$ and $V$ that follow the uniform distribution on $\Omega=\{1,2,3,4,5 \}$.
Let $Y=max(U,V)$

What's the joint distribution of $(U$ , $Y)$?

Answer : The joint distribution is expressed as follows

My question: Can someone explain to me the values on the diagonal? I get why we have $0s$ because those events are impossible but I don't understand how did we get $\frac{2}{25}$,$\frac{3}{25}$,$\frac{4}{25}$,$\frac{5}{25}$

Solution 1:

Note that $$ P(U=k, Y = k)= P(U=k, V\leq k) $$ for $k=1,2,3,4,5$ since $Y$ is the maximum of $U$ and $V$.