The only way to know how many you own, regardless of being in or out, is through this value in the Classes tree.
Note that the options Availability and Usage, in Classes options menu, are related only to Bookings - not reflecting check ins/outs. When a member of a Class or the pure Class gets booked, the availability number goes down on the affected days.
In the Objects tree, the stock of a Virtual Object is displayed by mousing over the Dispatch Status icon. And if you add the Class to the Objects tree, the stock will show between brackets.
But here there is no info about total owned.