You can sign into SmartDeploy.com and download a license report, which is a CSV file containing a list of all computers that have consumed a SmartDeploy license attached to your account.
In the Computer Management view of the SmartDeploy console, you can see a count indicating how many computers are currently in each group, including an overall count in the All Computers group.
These numbers will not necessarily be the same, because they are measuring different things.
The count of computers in Computer Management is simply the number of endpoints that have the SmartDeploy client installed, and which are communicating with that specific console. It is a count of online and recently online clients only. This means that you could, for example, set up another console instance on a different computer which would have a count of 0 in Computer Management, because none of your endpoints would be reaching out to it. This would not affect the number of licenses you are using.
A client appearing in Computer Management does not indicate any specific SmartDeploy license status, because installing the SmartDeploy Client onto an endpoint does not - in and of itself - consume a SmartDeploy license.
A SmartDeploy license is consumed by a computer if that computer has been reimaged with SmartDeploy or has performed some other console-initiated deployment activity (such as deploying an Application Pack, Driver Update, or User Data Capture or Deploy).
How does decommissioning work?