The difference is $1,400. That is the amount of the 3rd Stimulus payment. Did you already get the Stimulus payment they sent out last year starting March 2021? Do you have 1,400 on 1040 line 30? You might have tried to claim it again. Line 30 is only if you didn't get the full amount or qualify for more.
Did you get IRS letter 6475 saying what they sent you? If you didn't get the IRS letter 6475 saying what they sent you then check your bank statements or Check your IRS account (both accounts if married) to see when and what the sent you.
Your Online Account | Internal Revenue Service
If the IRS thinks they sent it to you but you didn't get it request a trace for a missing third Stimulus payment
https://www.irs.gov/newsroom/questions-and-answers-about-the-third-economic-impact-payment-topic-j-p...
