After you file

I got the same notification from IRS today, after I came back to check my  SCHEDULE 8812,  I noticed this

look like IRS is expecting the highlighted cell would be 1,000, not sure why.  

In addition, after I reviewed this table again,  I found, maybe the data generated from turbotax is not correct.

I have 2 children, one is 14, another is 2, so my understanding is 4a would be filled in 2, and 4b would be filled in 1, 4c would be filled in 1, and 6 would be filled in 0.

can someone help to check if my understanding is correct?