Lease Breakage rule in VIrginia?

They are tacking on 600 bucks, likely under that "other concessions". That means that at sometime, likely move in, you were given a $600 incentive concession, in the form of a rent discount. It could even refer to a discount given to lease holders over month to month tenants. Ask them to spell out how they came to $1500, they should have it doented.