See the attached screenshot from iOS9.1 on an iPhone 5c. Note that it says my best mileage is 5.9 L/100km yet right about it says I just did better at 5.6L/100km.
Currently the app is using MPG logic where a higher number = better fuel economy. We know that isn't the case with L/100KM. It's been fixed in this upcoming update. It should be submitted to Apple today and hopefully out to you all soon (~6-8 days).