Why Am I Penalized For Annual Income?

I was covered by Covered CA for 6 months of last year as my income had been cut in half and I became eligible for a subsidy. Now I am being told that I have to pay back all of the subsidy because of the amount of money I made for the entire year. I would have been better off just not having coverage and paying the penalty, especially since I never even used the coverage I had. How is it possible that I can be penalized for money I made after I had cancelled Covered CA as soon as I was reinstated to full time with benefits. A portion of my income from last year was money I had to take out of my retirement account to pay what I owed to the IRS from the previous year. This is not right to penalize me based on income earned after my coverage had already been cancelled.