Am I supposed to elect federal income tax withholding when removing excess contributions from a Roth IRA?

I recently had $4000 removed from my Roth IRA to avoid the 6% penalty, due to my MAGI range and allowed Roth Ira contributions.  I did not roll it in to a traditional IRA and instead had it transferred to my brokerage account.  When I requested to have the excess contributions removed, they asked me if I wanted to either A) NOT withhold federal income tax, or B) specify the % of federal income tax I wanted to be withheld.  My understanding is that I do NOT want to withhold federal income tax because my money I contributed to the Roth and then removed is already taxed.

Was I supposed to withhold federal income tax on the contributions I removed?  If so, how much?

BTW - this was all done with Schwab.  The form I used to fill out is available at the following URL (section 4 has the verbiage about federal income tax withholding):  https://client.schwab.com/secure/file/P-221581/IRA_Rechar_Excess_APP13581.pdf