Your conversion is required to be a proportionate mix of nontaxable and taxable amounts, so the calculation performed on your Form 8606 is correct. The nontaxable portion of your conversion is $8,012 * $8,000 / $8,032 = $7,980. That leaves $32 of the $8,012 conversion taxable and $20 of basis remaining in your traditional IRAs. Had you converted the entire $8,032 to Roth, that would have resulted in $8,000 being nontaxable and $32 being taxable.
