Fuel Gauge
 

I have an Audi A5 2009. I put 20 litres in yesterday, and another 20 litres today. In between I have only driven 30km. My fuel gauge has not moved up at all and has kept going down, and currently shows 0km to empty. Is this just a computer glitch? I usually fill it up but have limited money the past 2 days but there should have been close to half a tank with the 40 litres I have put in.
Thanks, Daniel