This number comes from previous entries made such as a W-2.
The Retirement Savings Contribution Credit is available to you for contributions made to various types of retirement accounts. These include IRA's, ROTH's and 401(k) contributions as well as other retirement vehicles.
Your credit can be 50%, 20% or 10% of your retirement contributions depending on your Adjusted Gross Income.
I've inserted an IRS link that may be helpful I understanding this credit:
https://www.irs.gov/retirement-plans/plan-participant-employee/retirement-savings-contributions-save...
