Wrong calculating after partial fill up?

Hello, 

im new in world of Fuelio, im trying to switch from previously used fuel consumption webpage to this app. 

Im OK with importing old entries. 

But. 

When partially filled-up, the counted consumption is OK. 

The first full fill up after partial fill is wrong, it shows extreme consumption on that entry. 

For example: 

70liter tank
At 239414km partial fill with 20liters, agter fill up 50% in tank. Consumption OK - 8,28l/100

239496 km full fill (54,17liters) to 70liters. At this entry i have 23,38 l/100 consumption, that is wrong. Correct should be  9.94 l/100. 

Why im having wrong consumption on every full fill after partial fills? It looks like its not counting with the partial fill up, or?

Thanks, 

Tomas