The AAP says 16-24 ounces, so you would be ok to add another 8 ounce glass.
BUT - these are simply guidelines. You know what is right for you lo.
If you lo wants more milk, and is still eating enough "real food", give them more milk.
If they are cutting back on real food and drinking more, I'd limit their milk so that they get enough nutrients from their food. Does that make sense?
You can also count things like yogurt, cheese, pudding, etc. as "milk" products.
And as long as they are under 2, IMHO, I wouldn't limit too much at all! If they want milk, give them milk (assuming they're not "drinking their meals"), if they want a snack, give them a snack! Under 2, they need about 1300 calories a day, and half of that should be from fat.
Obviously we want our snacks and meals to be healthy, I'm not talking about giving the child cookies whenever they want! :shock:
HTH!