Purchasing 3-Computer License will give you three more authorizations on top of the original one, i.e. a total of 4 computers on which you can use.
When purchasing 3-Computer License, please be clear:
1). The 3-Computer License is valid for the same period as the purchased product.
2). Device authorization is divided by Computer Operating System. 3-Computer License for Windows systems cannot be applied to Mac OS.
3). You can confirm how many computer licenses you have on Member Center > Lisence.

Extended Download Service ensures you be able to download (at Member Center > Extended Download Service) the standalone offline installer of nearly each and every history official release, whether minor or major version, anytime later just in case you need to reinstall a particular version of the PlayerFab software you've purchased. If you don't choose this service, you can still re-download that specific version when you purchase, but only for a limited period of time until a new version comes out. With only $9.99, that limitation will be lifted for good, you can redownload any official release anytime you want.