That suggests the dash readout is inaccurate on some
cars (and that instead of 'maximum' the instrument should say 'high' or 'excess'), but I've checked mine repeatedly and 4 bars = top mark on the dipstick. It goes down to 3 bars first start after an oil change, just filling the new filter is enough to lose 1 bar, and as I said, +500ml lifter treatment took it from 4 to 6 bars. So it seems quite sensitive, with 1 bar = ~250ml. It's not upset by camber either. I've not had a different reading from level on either side of my strongly cambered road.
My previous Renault had a similar system and that was also spot on, and I really liked the feature so I went to some trouble to check the Alfa system was trustworthy. When I collected the car I assumed 4 bars meant 'a bit low' until I read the book and checked the dipstick. On my car at least, it seems to be consistent and spot on.
EDIT: I just noticed the book shows a 6-bar display, so had to go and look at the car and the book is right. I can't count, it's 6 not 5
So I've just edited this msg to correct the numbers, 4 bars out of 6 = top level on the dipstick. Not that it makes much difference, it's the 2 blank bars on the right that I know to mean oil level is where it should be on my car. YMMV, of course.