Quick question about leasing a car

[drift925]

From what I've been reading, in simple terms, a lease equals:

Value of car - Residual Value = Amount being lease
$22,000 - $15,000 = Your payments based off a $7,000 difference for your lease.

Now my question is, what if the pre-determined residual value is wrong and the car is worth more at the end of your lease (due to market value, condition of car, miles on car, etc) what happens to the difference??