IRA Conversion to Roth - Addl amount removed for tax payment

Moved $35,000 from IRA to Roth IRA, and $4,000 was withheld for federal taxes. Turbotax is telling me that I will pay a $400 penalty for the $4,000 withheld. I did a similar transaction last year, but I didnt have any penalties for withheld funds. My income was lower in 2019 which might be part of the problem, but what can i do to avoid the penalty?