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. Check 1040 line 28 for it.
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...
