You would not owe a penalty for the last three months. The exemption code C means there is a short coverage gap of 3 months or less.

Per the State of California, you will have to pay a penalty, the Individual Shared Responsibility Penalty, when you file your state tax return if:

• You did not have health coverage
• You were not eligible for an exemption from coverage for any month of the year.

To confirm your penalty is correct, you can input your data into California's Estimated Penalty Amount. 

Lena,

I think you did not understand the question, or probably the wording of the question is too confusing.

Let me explain that I´m a software Quality Assurance Engineer and I find "defects" in software for a living.
Why wouldn't I owe a penalty for the last 3 months if I DID NOT have coverage and I should have had it? And why would the Exemption or Status of the last 3 months be affected by changing another month? (did you read the entire wording of my question?)

Please I'm trying to report a defect in the logic of the penalty calculator, I entered this question, not because I don't understand that I need to pay the penalty, I entered this question because TurboTax did not allow me to talk to a human agent that can actually help and report this bug to the TurboTax software development team. I hoped that this would be a way to get some visibility on this issue that I'm sure is affecting other people too, causing errors and making the CA returns to be rejected.