The sizes of the intersections of two unitals in PG(2,q2)

We show that the size of the intersection of a Hermitian variety in PG(n,q2), and any set satisfying an r-dimensional-subspace intersection property, is congruent to 1 modulo a power of p. In particular, in the case where n=2, if the two sets are a Hermitian unital and any other unital, the size of the intersection is congruent to 1 modulo q or modulo pq. If the second unital is a Buekenhout-Metz unital, we show that the size is congruent to 1 modulo q.