Look at the function. It's recursive. We write it mathematically as stated below.
$\mathrm{Count}(x,y)= \left\{\begin{matrix} \emptyset & y= 1\\ \mathrm{Count}(\lfloor \frac{x}{2}\rfloor,y) & x\ne 1, y\ne 1 \\ \mathrm{Count}(1024,y-1) & x=1, y\ne 1 \end{matrix}\right.$
It means the first parameter $x$ is being halved by every call until $x=1$. In fact, the first parameter $x$ is decreased geometrically (logarithmically based 2) like $(1024,512,256,...,1)$. On the other hand, the second parameter $y$ is linearly decreasing by 1 until $y=1$ like $(1024,1023,1022,...,1)$.
So roughly the number of times $\mathrm{Count}(x,y)$ being called $=O(\log_{2}(x)+y)$. More accurately it is $\log_{2}x +\log_{2}(1024) \times (y-2)$
$\therefore$ The number of times $\mathrm{Count}(1024,1024)$ being called is $$\begin{align}\log_{2}(1024) +\log_{2}(1024) \times (1024-2)&={\log_{2}(1024)}\times(1024-1)\\&=10\times 1023=10230 \end{align}$$
So the correct answer is $10230$.