The value of the seized property would be what it gets at auction, no?
Less the allowable costs of collection (sheriff fees, auction costs, etc) which can really add up fast. If real estate the auction price is generally subject to prior mortgages and liens, including property tax. Sale may or may not be subject to tenants rights under current leases. After the costs of collection balance goes to judgment holder (NY) with any excess to the property owner. There is little or no incentive for NY not to seize/attach everything possible.
If The Donald was a normal debtor it's almost certain that his mortgages would all contain language triggering a default on the mortgage in the above circumstances, even if Trump was current on payments.
This cascading set of events cries out for a bankruptcy filing-either voluntary by Trump or involuntary forced on him by his creditors. It is astonishingly pig headed or just plain stupid for him to follow this course of action.
The situation is, of course, complicated enormously by how Trump holds title-odds are he has a alphabet soup of LLCs, corporations, limited partnerships, etc. But remember NY already has a financial monitor in place so they have a pretty good idea how he holds things-probably complicated by a blizzard of transfers he has done recently (if transfer in fraud of creditors rights can be reversed by court).
Trump is certainly well versed in all of this, and he can hire the best lawyers possible. Whether he follows counsels' advice is up to great debate.