Petrol Gauge not working properly for honda jazz

[Pioneer]

I not sure whether can this be call a problem. But I realise for the last 2 mths..

 

My orange indicator lights up at 32L instead of 34L usually.

 

The only thing that I rem was that the undercarriage was hit by some humps recently.

 

Is there anything that can be done? Did my oil tank got smaller or that the indicator has spolit or sth?

 

Anyone have any idea?