The Form 1099-R is correct.
The $6,000 nondeductible traditional IRA contribution for 2021 was reportable on your 2021 tax return on Form 8606 line 1. This propagates to line 14 where it carries forward to line 2 of your 2022 Form 8606. Only the traditional IRA contribution for 2022 is reported as a new $6,000 contribution on your 2022 tax return. If you failed to report the contribution for 2021 on your 2021 tax return, you must amend to include the missing Form 8606.
Your 2022 Form 8606 will show $6,000 on line 1 and $6,000 on line 2 for a total of $12,000 of basis in nondeductible traditional IRA contributions to be applied in determining the taxable amount of your $12,000.12 Roth conversion (which TurboTax rounds to $12,000). With a zero 2022 year-end balance in traditional IRAs, the taxable amount on line 18 will be zero.
