Your Total Income can be less than your Gross Income if you had Other Credits and Deductions, in addition to subtracting the Standard Deduction (or Itemized Deduction).
Review the Schedule 1 and Schedule 3 forms in your tax return that will show any additional Credits and Deductions you were eligible for.
Since we can't see your tax return in this forum, if you want more help with your return, click this link for info on How to Get a Live Review .