The day after I got my car back from it's first (9000mi) service I got a low oil level warning. This was after my dealer changed the oil and presumably added to correct amount. The dipstick showed the oil was within the limits, but I added about a half quart to bring it up near the top of the range. Warning went away and has not returned.
The oil level sensor (on my car at least) is very sensitive to oil level and likes to see it near the max level to be happy.