You don't get to chose the code. You have to enter the code that is in box 7 of the 1099-R. Then follow up screens after the 1099-R data entry screen will determine if you qualify for any exceptions to the penalty. Do note that no matter what, the withdrawal is taxable income. But if you qualify based on how you answer the questions on the follow up screens, then no early withdrawal penalty will be assessed if the withdrawal was before retirement age.
Any taxability of the withdrawal will be offset in the Medical Expenses section, when you get to that point in the program. But that will only be true if the total of all your medical expenses for the year exceed 2% of your AGI *AND* the total of all your itemized deductions exceeds your standard deduction.
