The number of objects shown in the Control panel is defined by the current filter. You must enable the filter by clicking the button  (Turn filter on/off). The first drop-down list defines condition for filtering by alarms, failures, presence or absence of connection; the second drop-down list defines the condition Show only objects with errors for last...; and the third one defines the condition Show only objects with errors lasting longer than...

In the window's upper-left corner, you can see the two numbers: 1) the total number of objects and 2) the number of objects shown in the Control Panel after you click the  button.