- run Update Manager as superuser, e.g., `gksudo mintupdate`
- wait for the GUI to appear and for the updates to download
- hit the top-row button="Update Pack Info"
That will tell you
- what Update Pack you have
- what is the latest available Update Pack
However, I strongly suggest that the mintupdate developers refactor this software to separate commandline and GUI. With that, tests would be easier to automate, and it would facilitate enabling folks to answer simple questions like this via a simple commandline invocation, e.g., `sudo mintupdate --up`. (If this capability is already available, please lemme know.)