Arriving 20% SOC higher than predicted

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Couple of longer drives in the uk recently. From starting 100% charge arrived at 40% rather than ~20%
predicted by the app.
The car is returning ~3.4miles per kWh and the app is using 3.38 miles per kWh so that does not explain the difference.
Basic version of the app. With 20% extra charger it’s just not optimal charging.
Had a headwind on the trip so wasn’t that.
Can’t see any other settings to bring this accuracy in ?
Car is Kia EV6 and using the shared EV6/Ioniq 5 profile.
Same route predictions iphone app and internet.