Question as result of filing

I filed the 2019 return.  I answered the question regarding the Covid relief payment.  I entered $2400.  Once I did that, it upped my refund from $36XX to $48xx.  That should not have happened.  I then got a letter from IRS regarding this but it is unclear as to what I need to do.  I looked in the TT file and it shows a "Recovery Rebate Credit Worksheet.  It says I get a credit of $1200.  Why?  That should not be.  What do I do to rectify this?

 

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