How do I retain my license installation count or avoid error of “Exceed Activation”
If you don't uninstall the application from old machines and keep reactivating them to the next machines after certain such instances you'll get the message you've reached your activation limit.
As the retail license policy, it should be installed on one machine only however if there is a requirement then it can be installed on another machine as back up, the important thing to note that it mustn't be used simultaneously.
For futher more information read EULA