chadbrucato, your Form 1099-R was not prepared in accordance with the instructions for Form 1099-R. Normally on a code J8 Form 1099-R the payer will not mark box 2b Taxable amount not determined and will include only the taxable earnings in box 2a, in this case apparently $585.87. If the Roth IRA custodian calculated the earnings, there is no reason that the Roth IRA custodian should have don otherwise.
The fact that box 2b Taxable amount not determined is marked seems to suggest that you did the earnings calculation and told them the total to distribute and they chose not to get involved in determining if your calculation was correct. If that's the case, it seems that they should have left box 2a blank.
If they did the earnings calculation, I suggest getting them to correct the Form 1099-R to have only $585.87 in box 2a and to have box 2b Taxable amount not determined unmarked. Otherwise, you'll need to submit a substitute Form 1099-R (Form 4852) to show this and provide explanation, which will require that you print and mail your tax return.
