Since $20k was withheld for taxes, if this was just the 20% mandatory withholding on amounts eligible for rollover, this would be consistent with a total distribution of $180k, with $80k being RMD, $100k being converted to Roth and $20k of the $80k RMD being withheld for taxes on the $100k conversion. With the entire $180k being taxable, $60k of marginal federal tax liability on $180k indicates a marginal tax rate of 33%, which doesn't seem particularly odd for someone who is subject to an $80k RMD (suggesting a relatively wealthy individual who could easily have enough income to be subject to that marginal tax rate). But this is just a guess.
[Edit] I'm not sure how I would explain only $20k being withheld if only $21k was RMD. If the rollover to the Roth IRA was a direct rollover, that should have been reported on a code G Form 1099-R separate from the code 7 Form 1099-R that included the distribution of the RMD.
