Each license comes with at least 3 activations. If you have multiple seats, each additional seat allows for 3 more activations.
When activating a 4th computer, you will be told you've run out of activations. To solve this, deactivate your license on your other machines or add a seat for three more activations.
If for some reason you're unable to deactivate your license (due to reinstalling your OS for instance), we can of course help you out by resetting your license. Just shoot us an email to do so.
open Preferences (Command-,)
Go to the License panel
Click the downward chevron next to Hedge in the top left
If needed, we can always help you out by remotely resetting the activations on your license. Just shoot us an email.