The amounts on lines 19 (Child tax credit) and 28 additional child tax credit), on form 1040, are attributable to claiming your son as a dependent. Most (but not all) of the amount on line 27 (EIC - Earned income credit) is because of the dependent. To see how much your EIC would have been without the child, see the EIC table at
https://www.irs.gov/instructions/i1040tt#idm140702909059168 scroll way down.
For example, at $15,000 of earned income, the EIC for no kids is $273, for one kid it's $4213. So, the kid got you $3940 of EIC (in addition to the child tax credit and the additional child tax credit).
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