AT&T Early Termination Fee Questions.?

I am currently in my iPhone 3GS contract with AT&T, and I am looking into switching to Verizon, as AT&T coverage in my are is deteriorating. According to the AT&T website, it costs $325 minus $10 for each full month of your Service Commitment that you complete. I have been in my contract since November of 2009, and do not feel like spending the next five months with my phone being useless in my house. My math could be wrong, but that would mean I am 19 months in and $325 minus $190 is $135. But I have a second iPhone 3GS on my account. Do I have to pay $135 per device, or $135 for both?