My Additional Child Tax Credit is limited based on 15% of my earned income, what does this mean in layman terms? I have 5 children but am only getting credit for 1.

Earned income is income earned from working a job or providing a service, either as a W-2 employee or by self employment/side gig.  The basic child tax credit is up to $2000, but only if you owe that much tax.  With 5 children, you would have to have more than $80,000 of taxable income to start coming close to owing that much tax/getting that much credit.    The Additional Child Tax Credit is money you can get for your child dependents even if you owe very little tax, and in that case, it is based on income earned from working, not income from retirement, prizes, investments, or unemployment compensation.  Turbotax will figure it all out for you.

Also, to be eligible for either the child tax credit or the additional child tax credit, the child must be under age 17 as of December 31, 2024; and have a social security number valid for work; and live in your home more than half the year; and be your biological child, your step child, your foster child, or your niece or nephew (children who are not related, such as the child of an unmarried partner who is not your child) don't qualify for these credits.