Currently Tylenol and other acetaminophen containing products come in two liquid doses: infant and child. The infant product is approximately 3x more concentrated than the children's. The dosing for the two is different, and it can cause some confusion. Over the next 6 months to a year makers of acetaminophen containing products will phase out the infant formulation and only have the child version. This will mean that when you give your baby Tylenol, you will give her a larger volume (but the same amount of medication because it is less concentrated) than you previously did.
Just to be clear, DO NOT give your infant a larger volume of the current Infant drops (80 mg/0.8 ml) than what you usually do. This would overdose the child. But once the changes occur, the amount of Children's Tylenol you will give will be different. We will let you know when the changes start rolling out.
This is a pretty good chart for Tylenol dosing. It differentiates between Infant and Children.