It means TurboTax Online has computed that you owe $5 based on the information you submitted. Was the amount paid last year? You can get a transcript from the IRS and check to ensure you do owe the balance.
Here is some helpful information on obtaining a transcript: What is an IRS Tax Transcript and How Do I Request One? You can request a "tax return transcript" by phone or online.
If you're certain you didn't pay, and want to send the money owed, you can do so online at EFTPS or mail a payment voucher (Form 1040-V) to the IRS. The mailing address where you should send your payment depends on where you live, so check the 1040-V instructions here.
You can obtain the 1040-V from your 2023 TurboTax Online return. See: How do I get Form 1040-V?