The best way to get the uptime is from the appliance itself as it is windows based it would be any of the following steps below; as in windows.

I will submit a Feature enhancement to see if it can be added to the appliance screens of the UVM’s to be included with the status of services. 

• Task Manager
Open the Task Manager, then navigate to the Performance tab. Under the CPU section, you'll see the "Uptime". 

• Command Prompt
Use the systeminfo command to get a list of system details, including the "System Boot Time". 

• PowerShell
Use the command (get-date) – (gcim Win32_OperatingSystem).LastBootUpTime to see how long it's been since your last restart.