If you are receiving a refund or low tax due and TurboTax prepared the vouchers then your tax liability was probably reduced by credits. Your Tax Liability is the amount on 1040 line 12b. It is the tax you owe on your income. But you might qualify for credits that can reduce your tax due or even give you a refund.
Turbo Tax is very conservative and doesn't want you to owe next year. They might have printed out if you got a big one time increase in income. like if you took a IRA or 401K Withdrawal or had a big stock gain. They are optional to pay. They don't get sent in with your tax return so the IRS won't be expecting them. You can ignore them.