I'd Hate to Be Confused with Numbers

So when I was in Macey's the other day buying groceries, I happened to notice the sign on the counter warning guests that those under 30 would have to have their identification, if they were buying something that required identification. However, they had the 30 in quotes. As in,

If you are under the age of "30."

Is there a different 30 that isn't a number or something?