Bitul and kosher food

Question

Aunt Jemima Original pancake/waffle mix was originally labeled as 'O-U' until a month or so ago. Now it is listed as "O-U D", but the ingredients contain NO milk products. However, there is now a statement on the box saying "May contain traces of milk, egg..." The word 'May' implies uncertainty that milk is present, yes? How, halachically, does 'May contain traces of milk..' render the product 'dairy' in the opinion of the O-U?? How does the concept of bitul work when dealing with KOSHER ingredients? For example, how much milk would I have to add to a 'parve' cake batter to render the batter 'dairy'?