Only the $36,000 shown in box 5, not $70,000, is after-tax money.
"why would the $30,000 go to the Roth?"
If it went to the traditional IRA, that money would have been nontaxable and not included in box 2a. Because the $30,000 is being reported as taxable, it means that the payer is reporting is as having gone to the Roth IRA, effectively as a Roth conversion. If the payer believed that $70,000 had gone to the Roth IRA, the taxable amount would properly have been reported as $34,000 (so that when added to the amount in box 5 the total would be $70,000).
If there was any rollover of designated Roth contributions, that would be required to be reported on a separate code-H Form 1099-R as DavidD66 indicated, but the fact that it was all reported on a code-
G Form 1099-R implies that none of this came from a designated Roth account and that the after-tax money was in the traditional account, something that is entirely plausible. Of course the payer could have botched the reporting, but there is no way to know that from the Form 1099-R itself.
