Mil gave 4 week old Advil, ok?

She was watching him for me & he's been pretty fussy so she gave him Advil. I saw the box & it's labeled to give to a 6 month old. Is it okay she gave to a 4 week old ? Is it bad ?
What do I do? I'm so scared 😫ftm mom. She says its fine because it's a small dosage.