The number displayed in parenthesis next to a Class in the Classes tree shows the total number of Objects that your company owns. This is particularly useful for Objects configured as "Virtual Objects" and as "expected to be returned when checking out" (as opposed to Virtual Objects configured to be sold - see more about this here).
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.
