The code 2 is correct. Code G is incorrect.
The taxable amount must be calculated on Form 8606. Either you've provided TurboTax with an incorrect amount for your basis in nondeductible traditional IRA contributions, resulting in an incorrect calculation on Part 1 of Form 8606, or you have a nonzero year-end balance in traditional IRAs, causing your Roth conversion to be largely taxable because only a small amount of your basis applies to the Roth conversion.
