If I understand you correctly, you were going to default on your lease so you returned the car back to them. And now you are being faced with a charge you do not understand.
Allow me to explain, I may be wrong so I would advise to go over your original contract. When terminating your lease early you are responsible for any fees and penalties. This includes a very important factor called the residual value. When you obtained your lease they estimated the residual value of the car, the higher the value the lower your lease payments would have been. However there's a downside to that after voluntarily surrendering your leased vehicle, the bank or leasing company sells it. Usually, the vehicle is sent to a dealer-auto auction. Once the vehicle is sold, the net proceeds are applied to your balance at the time of surrender. This balance is not the same as your lease-end residual balance; it equals the lease-end residual plus the remaining payments on your lease contract.
In short, don't default on a car lease. Especially when car prices have dropped which means your car depreciated much faster over the years.
What you should do now depends on your current financial situation. Your credit score is probably very poor so trying to finance out of it will be difficult and it's ill advised unless you want to make 15-20% interest payments. If you have little assets i would declare bankruptcy, but please do check the rules in your province and know how you would be affected before doing so.
Canadian Investor
http://canadianpersonalfinance.blogspot.com