Yes, this has been discussed before and it is well documented. My 2011 Elantra does the same thing. The mpg gauge always reads ~2 mpg high, so while the gauge is inaccurate, it is consistent. Just subtract 2 for the "real" mileage.
If it makes you feel any better, a lot of other cars do it. My wife's old Malibu did the exact same thing (optimistic by 2 mpg), so this isn't just a Hyundai problem. However, I'm not naive, and I think, actually I know, Hyundai knows about it and could do something, but they don't. I'm sure they're more than okay with the mpg gauge being slightly optimistic.
With all that said, my wife's 2013 Altima seems to be spot on. Her gauge is very close (within .5) of what the actual mileage is. Plus her car actually hits its fuel economy rating (38mpg) in only 75% Highway driving. It sometimes pisses me off that her car has more power, weighs more, is bigger, is quieter and yet gets better gas mileage.

Whatever, I trust my drivetrain more (not sold on CVTs yet).