You can manage the number of Device Licenses you have from the Device Licenses tab on your Settings page (i. you can get to the settings page by hovering over your name in the top right corner).
You will be instantly prorated for any Device Licenses that exceed the number you paid for on your last invoice. If you remove enough Device Licenses so you have less than you paid for in your last invoice, you will still have access to the number you paid for until the end of the current billing cycle. You will be charged for the new amount of Device Licenses on your next invoice.
