Technical explanation commences:
You may activate your license simultaneously on three (3) devices. A device is either a computer or a USB-drive. You may also deactivate the license from previously activated device. The number of different devices that have been activated during a timespan of one year may not exceed six (6).
Example: First you activate your license on one device (A). Few months later, you’ll decide to activate your license on two more devices, (B) and ©. You then deactivate all of those, and activate your license on three other machines (D, E, F).
At this point, you can deactivate any of the recently activated devices, and reactivate any of the previous devices. So the devices (A-F) form a pool of six devices.
To activate the license on a new, previously unactivated device (G), you’d have to wait until one year has passed from the initial activation of (A). You could then deactivate one active device from (A-F), and activate (G) instead.
If you deactivate (A) after more than a year has passed from its initial activation, (A) will be removed from the device pool. If you now reactivate (A) after it has been removed from the pool, the activation time of (A) will be reset to now.
So in short, the combined number of activated and deactivated devices per license during one years time may not exceed six.