$20 Old Navy Certificate for $10

Groupon is offering a $20 Old Navy certificate for only $10, but hurry, quantities are limited!
Fine Print: Valid from 12/22/11-1/28/12 at US Old Navy Stores only. Good for $20 of merchandise: $10 Paid For value (never expires) plus $10 Discount Offer value (expires 1/28/12).