I have only had a child during the time that 100% of the credit was refundable so I am unsure how to do the math with this current situation. Can someone walk me through it?

I

*think* (and therefore put this logic into the current case study spreadsheet) it will be

a) subtract up to $2000/child from the "tax due minus (up to $500/dependent-not-eligible-for-the-CTC)"

b) get a refund of up to $1400/child minus the amount used in "a".