Your confusing three credits; day care, Earned Income (EIC) and Child tax Credit.
$606 = $4040 x 15%. That tells me you had $6540 (4040 + 2500) of earned income. If that is correct, then $606 is the correct amount of (Additional( Child Tax Credit. With $6540 of earned income and one cjhild, you should also get $2219 of EIC
