529 plans are not like a Roth IRA where you can split principal and earnings. Everything is proportional.
By withdrawing the full $210,000 you will be taking a $10,000 qualified distribution and a $200,000 non-qualified distribution.
Of the $10,000 distribution, $476 will be earnings and $9,524 will be principal.
Of the $200,000 distribution, $9,524 will be earnings and $190,476 will be principal. The $9,524 will be subject to ordinary income tax at the recipient's rate, plus a 10% tax penalty. So, assuming you are in the 24% tax bracket, you will pay $3,238 in federal income tax. In addition, there will be state income tax on the $9,524, plus recapture of any state income tax breaks attributable to the distribution.