Number of distinct possibilities for $xy$ such $p$ and $q$, odd primes, $p-x|q-y$

Question

Background :

Let $p, q$ be odd primes such that $n=pq$

Let $x, y$ be integers such that $0 \leq x < p$ and $0 \leq y

Let $a=xy$

If $p-x\mid q-y$ then $p-x \mid n-a$

My question is : is there a way to estimate the numbers of distinct values of $a$ such $p-x\mid q-y$ knowing only $n$ (not $p$ and $q$)?