Gain carried over from one TRAC lease to another

We have a fleet vehicle leasing agreement with a TRAC (terminal rental adjustment clause), whereby at the end of the lease, the leased vehicle is sold. An expected residual value is stipulated at the beginning of the lease term. If the vehicle sells for less, we make up the difference. If it sells for more, the excess is given back to us, in the form of a reduction in rental cost on our next vehicle. The leases are capital for book purposes. When there's an excess, I'm not sure how to properly record the carry-over from the sale of the original vehicle to the new lease. Let's say it's a $2000 refund. Should I reduce the fair value of the new lease by the $2000? The cash outlay on the new lease will be reduced, so if we don't reduce the fair value, we'd end up with an extra-low interest rate that doesn't reflect how the lease is actually calculated. But I feel like the $2000 shouldn't just disappear; there ought to be some entry that reflects the original sales transaction, even if it's then used in some way. If the refund were given as cash, we'd record $2000 cash debit, $2000 gain credit. What would be the next step from there to apply the cash (which in this case isn't actually received) to the new lease, and presumably eliminate the gain as well?