If you have two or more children in daycare then the maximum amount of expenses, you can count in claiming the credit, is $6000 ($3000 for one child).
So, even though you spent $15,000, you may only count $6000 (or $3000). The credit percentage is looked up on the table on form 2441 (https://www.irs.gov/pub/irs-pdf/f2441.pdf).
So, for someone with an income (AGI) of $140K, your credit is 20% of either $3000 or $6000. That is $600 for one child or $1200 for two or more.
