TurboTax is calculating both credits correctly. Maryland does not have the age requirements that the Federal Earned Income Credit does. I pulled this quote from the Maryland comptroller's office:
Employees who would otherwise qualify for the federal credit but for federal requirements excluded from Maryland law may claim the state earned income credit by calculating the federal earned income credit disregarding those requirements. There is no minimum age requirement for taxpayers without a qualifying child, nor must taxpayers have a social security number to qualify for the Maryland credit. Additionally, certain employees may also qualify for a refundable Maryland credit or a local EITC.
Federally, you would either have to be over the age of 18 or over 24 if a full-time student.
