Schwab's "experts" are apparently not taking into account that you have $10,000 of other funds in traditional IRAs. Because you had $10,000 in traditional IRAs at the end of 2023 (Form 8606 line 6), only about $2560 of your $6,500 Roth conversion will be nontaxable with about $3,940 your basis in nondeductible traditional IRA contributions remaining in your traditional IRAs to be applied to future traditional IRA distributions (Form 8606 line 14).
