Hey don't worry about those devices showing. They will go away from your device list. You will still see multiple device installations on your My Grid page, but it doesn't mean anything. I have probably dozens of devices installations listed that are no longer there, but only a handful of computers actually crunching. If you ever have to uninstall and reinstall the agent on the same computer it will make a new device installation. It won't matter if you have 1 device or 1,000 (or more if you are lucky and have a whole fleet of computers to do some crunching). Good luck and happy crunching.
If you have more questions feel free to browse the forums, check the Start Here forum, and if you still don't find anything, ask!