If you claimed an adult dependent you get the $500 credit for other dependents. You do not mention your sister's age so we do not know if she is a child or an adult. But the "child and dependent care credit" is a credit you can get if you paid someone to take care of your dependent so you could work. Did you pay for some sort of care for you dependent so you could work?
Do you see the Credit for Other Dependents on line 19 of your Form 1040? It is a non-refundable credit that can lower your tax owed.
PREVIEW 1040
https://ttlc.intuit.com/questions/1901539-how-do-i-preview-my-turbotax-online-return-before-filing
CREDIT FOR OTHER DEPENDENTS
https://ttlc.intuit.com/questions/4499708-what-is-the-500-credit-for-other-dependents-family-tax-cre...
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