Review the Calculations:

From his aunt, Andy received 4 teaspoons of infant's formula at 500 mg per teaspoon = 2000 mg acetaminophen

Because 150 mg/kg body weight is an overdose, the level of acetaminophen that would be an overdose for Andy is found as follows:

150 mg/kg body weight x 12 kg = 1800 mg acetaminophen

If the aunt had correctly used the dropper for each dose, Andy would have received only:

4 droppers of infant's formula at 80 mg per dropper = 320 mg per day