As you walk through the questions after his name, make sure you selected that he did NOT provide over half of his own support.
As a 22 year old, he would only be eligible for the $500 Non-Refundable Other Dependent Credit, not the $2,000 Child Tax Credit.
You can see the Other Dependent credit amount received on line 19 of your 1040. To see your 1040 click Tools>>Tax Tools>>Preview My 1040.