Confused? I admit that's a complicated headline for a Monday morning, so let me try again. Tomorrow, March 20, you can pay $5 and get a $10 Amazon store credit. They're doing this to promote their own daily-deals site (like Groupon), but you can spend the credit anywhere on Amazon.com - it doesn't have to be on AmazonLocal.
They're being a bit coy about how many of these deals are available, but I have a feeling they'll be server-crashingly popular, so stick with it if you have a little trouble tomorrow!