Here are the details straight from Amazon.
Get a $10 Video Games Credit
Order Final Fantasy XIII and get $10 off a future video game purchase. The promotional code will be placed directly into your Amazon.com account within 2 business days after the product ships. Offer valid when shipped and sold by Amazon.com. Promotion valid on all existing orders. Limit one per household. Amazon reserves the right to change or terminate this promotion at any time.
Not a bad deal since there are a ton of other games coming out in March this credit could be used on. Even though the PS3 box art is pictured, the promotion is valid on the Xbox 360 version of Final Fantasy XIII too.