reports consumption

Hello My w203 with 200cdi spends 7 liter for 50 km in Urban street, and for 100 I can spends 14 litre, 14 l/100 km(urban). But in display say 8.7 l/100 km, and the report is 13 km/hour. I put in computer and no problem can find. Have any Idea for this, but I ask for this cause and nobody hear...