Extra Withholding

My wife and I work for two different companies, and Federal and State taxes are deducted from our respective biweekly paychecks.

 

Per the instructions in Form W-4, we used the Deductions Worksheet to determine and specify the amount of extra withholding per paycheck.

 

Given that taxes are deducted from our paychecks, does there need to be additional withholding?