Why is the first child 2000$ but the second is 500$?

[stanfieldalexis]

first child born 2017 and second was born 2020 (so 2020 was first year for the second child being added to tax return.)

[SweetieJean]

Are you asking about the Child Tax Credit?

[Hal_Al]

When asked how long the 2020 child lived with you, answer all year, per the instructions for newborns on that page.