$100 Back to School 2012 gift card

What am I allowed to purchase with my $100 Back to School 2012 gift card?

I am trying to buy a case online for my new Macbook Pro with my given $100 gift card but am having some difficulties. When checking out on the Mac Store you are asked to provide the card and pin number of gift card, but I'm not sure which numbers to use ~ I've tried several combinations...

• 16 digit code on the top right (numbers/letter)
• 6 digit code on left of barcode (numbers)
• 4 digit code on bottom left (numbers)
• 22 digit code centered on bottom (numbers/letters)
• 11 digit code on bottom left (numbers)

I redemed my card in the app store perfectly so I know it is valid but don't know how to use it in the Mac Store or that is even possible...

Help!