That's a great question. The answer is subtle.
While you have paid enough estimated taxes, you probably didn't pay it when the "regular" calculation method says you should have. By default you must pay 1/4 of the total amount each quarter. You cannot wait until the 4th quarter and pay it all. If you do that the other quarters appear underpaid and you are charged interest by the day.
The solution is to not use the default method of computing required payments and dates, but rather to use the annualized income method. However, that is very complicated. It involves figuring your income and deductions separately for each quarter (mostly). Turbotax does support the Form 2210 Schedule AI that you need and will walk you through it. See this older post about how to go through that. It may not be worth it if the interest/penalty is small, but that is your call.
https://ttlc.intuit.com/community/retirement/discussion/my-tax-penalty-is-calculated-as-if-my-income...
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