It’s a "non-refundable" tax credit, which means that it can’t reduce the amount of tax owed to less than zero, so it won't necessarily increase your refund.
The so-called "Saver's Credit" is calculated on a specific percentage of the contributions you've made during the year, with the percentage based on your adjusted gross income.
Please see the TurboTax article "What is the 2019 Saver's Credit?" for more information.
I'll also attach Form 8880 so that you can see how the calculation works.
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