Range of markings on dipstick:
WARNING: This page is about a different car, the 2006 Audi A4, 2005 Audi A4, 2004 Audi A4, 2003 Audi A4, and 2002 Audi A4. However, it is still accessible from the selected car via links, so may be relevant.
a - Oil must not be topped up.
b - Oil may be topped up. After topping up, oil may reach range -a-.
c - Oil must be topped up. After topping up, it is sufficient if oil level is somewhere in range -b- (shaded area).
NOTE:
Oil level must not exceed mark -a- on oil dipstick.