How Much To Mail A Letter These Days ?

I won an auction on ebay for some $3 Stamp. It arrived today along with a message from the USPS.

Observe cover



Postage due .20¢ ????



And the 2012 edition of Postage due, an envelope that I need to put .20¢ in and stuff it in my Mailbox for the Mailman. The cover is franked at .45 1/2 ¢ so I don't see an error on the senders part.

The names have been hidden to protect the innocent via my mad skills with Microsoft Paint....