Deductions & credits

I have to pay first in order to see my 1040 and I'm not doing that unless I feel that the answers are correct.   What I see when I look under deductions and credits for the line labeled Advance payments, Child and Other Dependent Tax Credits, is a 2021 item for $4,800.  This is the amount I entered in from my letter 6419 for what we received as part of the advance payment.  However, if I am understand CTC correctly, I am entitled to another $4,800 dollars.  My total CTC for 2021 should be $9,600.  

 

I did a test to get more info.  When I am inputting the CTC data, if I say I didn't receive anything in advance my, refund is sitting $6,421, and 2021 CTC is showing at $9,600.  When I say that I received by $4,800 it drops to $4,800.  What I am confused by is that I received a full $4,800 dollars from the Federal government in advance.  Why would I not be receiving the remaining $4,800?  Why is my refund dropping all of sudden to $1,621.  What happened to the other $4,800 dollars?