There could be a number of reasons. Each time you do reinstall or update OS of your device, do a factory reset, etc., the Unique Identifier of the device may change and our system will detect it as a new device. When you generate manual configuration settings, a new device is also automatically added to your Devices list.
You can manage your devices in your User Office and remove one device per week, or contact us to get assistance with your device list.
If you want to extend the number of devices on your account, visit this page.