There's not a numeric value to enter; you'll enter the name(s) of each person for whom you're claiming the credit for other dependents (ODC).
To see which, if any, of your dependents qualify, please see the qualifying requirements in the dropdowns for Qualifying child and Qualifying relative in the TurboTax Help article What is the $500 Credit for Other Dependents (“Family Tax Credit”)?.
If any of your dependents qualify, you'll enter their names in line 13.
