Just had this issue - car said add 1 litre, so I did. Did not take photo (with time stamp) of the car message. Lesson #1. Lesson #2 is: if the car says add another litre in an unrealistically short time from a recent oil change, don't. Turn the car off, wait half an hour, and restart, ensuring you are on a level surface. If you can afford to, my dealer said to wait > 6hrs as that is when the car 'goes to sleep' and stops looking for a key (Comfort access I think). My last oil change was 3k km ago, and I went and drove the Nurburgring F1 track (wet) for 40 mins - end of the session, the car said it needed oil. Fact is, it didn't. One minor overfill later, and the embarassment of 'fessing up to my SA and my M-Flight brethren, I have learned a couple good lessons.
In talking with others, I think if you have BMW dealership closeby, and you can afford the time (I know, rarely), take the car to them, ask them to top it up, and they can make the assessment, that way you are covered warranty-wise...
My 2 cents...
•'08 M5 Sepang Bronze/Sepang Bronze Full Merino leather w/ Executive Package/H&R/DINAN/20" DPE
•'12 M3 Coupe Space Grey on Silver/Black Novillo/M-DCT/ZCP/ZPP/M black grill/M Perf exhaust, CF splitters & spoiler, alcantra steering wheel, full CF interior trim
•'06 X5 4.8is Silbergrau/Cream leather fully loaded, stock