question about oil overfilling

what effect will have on the car if my oil level was about 1/4 of an inch above Full level on the dipstick ? I let the car sit over night before I take measurement.

I bought the car new back in April 08, 08 touring #6, the oil was overfilled from factory day 1 by about 1/4 of an inch, since I have no problem getting 48-50 MPG in LA, I didn't bother to take it in at that time.

Now the car is at 5000 miles, I took it in for its first oil service at the dealership yesterday, I told them about the overfill problem, they document it on the write up, but to my surprise, when I checked this morning, it was again overfilled about 1/4 inch above the Full mark on the dipstick, I can tell they changed the oil since the color is much transparent. I drove the car about 30 miles last night, still getting about 50-51 MPG.

My question is, should I take it back in have them correct the problem since MPG still seems to be ok ?