Remember that the discount requires a code, which may take anywhere from a few hours to a day or two to hit your inbox once you request it. Once you do, you can take that sweet quarter chunk out of the considerable price of the premium tablet, in either the 32GB or 64GB flavors. Unfortunately that doesn't apply to the Pixel C's neat induction-charging keyboard, but the discount should let you buy it more or less for free if you really want to.
The discounted price is good until July 15th or "while supplies last," which depending on your local country and Google's stock, may be sooner than you think. Get an order in soon if you want one, and only one, since they're limited to one discount code per order.