Turbo tax states that the standard deduction applied to my grandaughter's tax return is $12,200 instead of the correct amount of $14,600. Why the lower amount?

Is she being claimed as a dependent on someone else's tax return?

The standard deduction amount for an individual who may be claimed as a dependent by another taxpayer cannot exceed the greater of $1,250 or the sum of $400 and the individual’s earned income (not to exceed the regular standard deduction amount of $14,600).

Actually for 2024…..The 2024 Standard Deduction for an individual for whom an exemption can be claimed on another person's tax return is limited to the greater of:

…..$1,300 or

…..Your earned income for the year + $450 (but not more than 14,600)

So you would get a minimum of $1,300