I'm a bit confused by what you're stating.

Here is what I come up with for your car assuming a February Turn-in:

Baseline Buyback Amount with no mileage Adjustment (includes restitution) = $23,267

Options = $0 since its a loaded SEL

Mileage Adjustment = 87100 - (17months x 1042 miles/month) = 69,386 miles for a deduction of - $1,740

Total buyback based on Feb turn in would be $23,267 - $1,740 = $21,527

Which happens to equal $15,450 + $6,077 = $21,527

So what they are quoting you sounds exactly correct for your car.

The offer letters break it down by the Vehicle Return Amount, which is the NADA book value from Sept '15 and the restitution value, which is also adjusted based on mileage. VW does use the mileage you entered when registering on the website to estimate the turn-in number, so your offer is already adjusted for the 87,100 miles on the car. If you drive more or less than 1042 miles per month since you first registered the claim, you may fall into another mileage bracket which will result in a final higher or lower number than the offer estimate. They use 5,000 mile increments for each adjustment. Keep that in mind since you're bouncing around the 70k mile number after adjustment.

In your case you see the following which jibes with your total buyback offer.

**$15,450.00 Vehicle return amount (NADA mileage adjusted value)**

$6,076.73 Additional Restitution (Mileage adjusted restitution payment)

_________________________

total = $21,526.73

If you opted for the fix assuming it ever happens, you would receive the $6,076.73. The tables can be a bit confusing because they include the restitution in the total figure.