AVG Anti Virus installation

I bought the AVG Anti-Virus from the store, brought it home and tried to register it so I could get the License Number but when I type in the sales number it tells me "Your AVG Sales Number has already been registered in our database".  Why is this?

Lyndsay,

Sorry for the inconvenience caused. We need to enter our full license number to activate your AVG program. Once you register your sales number, you will receive the full license key. We have sent your full license number to your registered email address.

Please activate it as suggested here: http://avgclick.me/ActivateNewLN. Please, feel free to let us know if you require any further assistance. Thank you.