You do not need to do anything with stock in Virtual Locations. These quantities are not in your stock.  Only stock in internal locations hold your actual stock and have value.

Odoo uses virtual location to post stock movements in and out of your actual stock.  When you receive from a vendor it post out of virtual stock/vendor.  There you can see a big minus qty.  When you send to customer it post into virtual stock / customer.   And the same for inventory adjustment.  When you increase your stock with an Inventory adjustment transaction, it post a minus from Virtual Location / inventory adjustment. 

But another question you should look into: Why do you have so much inventory adjustment?