The DD code is the amount that your employer spent for health insurance. In any event, it does not affect your tax liability so just leave the amount blank. Since your retirement contributions are not voluntary, but required, you cannot use the $3375 amount for retirement credit. However, the $298 for health benefit is deductible, if you itemize, as a medical deduction on Sch A but you can only deduct an amount of medical expense greater than 10% of your AGI.
