The license key and product code are a matched set. If the original code submitted had a 0 device count as indicated, changing it to anything else would invalidate the license key provided. The amount purchased should always be the number of devices submitted during license key generation, regardless of whether or not you are using that many at that time. This helps prevent unnecessary license/product code changes in the future except for increasing max devices which should only happen on purchasing of more devices.
I am currently awaiting confirmation on the devices purchased for this order and will send an updated license key for that device count.