Filing an amendment for a 1099C

I received a 1099c after filing my taxes. I received my refund and I am trying to do my amendment. My 1099c is for 3,000. My tax bracket is 12% and I figured I'd owe 360. I'm trying to amend but it's showing me owing 900 instead. I'm confused and really don't understand if maybe I'm just doing it wrong.