Gas gauge information?

Hello friends, my 2005 model 1.4 gasoline x-line car does not receive the last quarter of the tank when I get full of gasoline, and when the gas runs out, even the line below the zero is over. What is the problem?

Probably my bad teacher. Remove the hat of the indicator part, take out the glass and bring the needle to the right hand. The tank normally takes 50 liters. How many liters it takes when you complete it. When he runs out of gasoline, fulle takes a few liters. Around 50, the display is defective. talip206 2017-07-29 11:46:18

Thank you, my master, thank you so much, I will do what you say for information ...