Can Administering Advil Two Hours Apart Cause Serious Problems?

My sons father just gave my 4 year old son 10ml s of children s Advil along with 8ml s of amoxicillin for a throat infection. 2 hours prior to this I had just given him 10ml of Advil...however the dosage time frame for Advil is supposed to be 6 hours. Do I need to be concerned? Thanks, Jennifer.