Go back to the insurance company and ask them. They may have mis-labeled your distribution. OR, you may not have read the fine print breakdown between ROP and taxable interest. OR you may not be in a “withdrawal” program, which discriminates between the two categories. But as a general rule, a withdrawal is first taxed as income: If money is left in your annuity account, the IRS considers the first and subsequent withdrawals to be interest and subject to taxes.
Read the entire article about annuity taxation here.
Then go back and talk to your insurer about the details of your withdrawals.