Fuel consumption anomaly?

I was sure I filled the car with enough fuel , but it went to pit a lap earlier than expected.

Looking at the time table i believe there is an abnormal fuel consumption :

http://igpmanager.com/play/?url=race-result/535808/59804

average lap consumption 3,7 L but:

Lap 8 - 4.5 L Left enters pits

Lap 21 - 7.5 L Left enters pits <-- very strange

...Confusing...



So i look at the previous season results:

http://igpmanager.com/play/?url=race-result/530707/542484

and it was quite the same (lucky for no last lap pit)



Am I missing something?

Thank You

3.7*2=7.4

depending whether your pit box is before or after the finish line, your last stint may require extra fuel.