Check line 28. Line 28 is the remaining amount you get. Not the advance you already got.
Usually it's the same amount. Did you enter the advance amount you did get? Then the rest should be on line 28 if you qualify like if your income isn't over the max. Oh and your total refund isn't necessarily the amount of the credit. It either adds to your refund or reduces a tax due.
Before filing, You can preview the 1040 or print the whole return
https://ttlc.intuit.com/community/accessing/help/how-do-i-preview-my-turbotax-online-return-before-f...
It was probably added before you noticed. It was added as soon as you entered your children. Not later when you enter what you already got.
