Activating Windows Server 2012 R2 Evaluation version to Retail version

I have downloaded and installed the Windows Server 2012 R2 evaluation version from Microsoft's Evaluation Center website. We decided to go ahead and activate it to the full version. We bought a Windows Server 2012 R2 Standard DVD and attempted to use the Key provided with the DVD following the method described here: http://technet.microsoft.com/en-us/library/jj574204.aspx

Yes, I did notice the mistake in the instructions and instead of finding out my version, I used "DISM /online /Get-TargetEditions" command to be able to get the correct parameter for the version of Windows Server I intend to upgrade to. The result was "ServerStandard".

So now, the new command is "DISM /online /Set-Edition:ServerStandard /ProductKey: /AcceptEula". I get the error the product key could not be validated. Check that the specified product key is valid and that it matches the target edition.

Does this mean that I won't be able to use the key from the DVD? Are they not the same edition? If they are, how do I go about activating the server? If the key can't be used, does this mean I will have to make a reinstall using the DVD?

Excuse me if this sounds like a question that can be answered through a simple Google search, but believe me, there is very little documentation, and that's why I'm turning to you guys.