I May Have Given My Son An Extra Dose Of

I may have given my son an extra dose of cephlexin he's 8 months old he needs 3 times a day 7.4 ml for a skin infection on his eye I thought the pharmacist didn't give us enough because it does t look like there's alot left so if coarse I blame my self and think maybe i gave him an extra dose and that's why.. If I did would that have done damage to his belly?