How did you do in actual Wh/mi on your trip? The estimate takes into account not being able to regen a full battery, so if you get right on the highway, I'd expect actual mileage would be better. There might be other factors limiting the Wh/mi on the top end. YMMV.
First suggestion is that you immediately get TeslaFi or a similar subscription (yes there is a cost) which will log charging and drive data for you and presents it in useful ways.
When one throws out km or miles to quantify charge levels confusion often arises because the car's estimated range is its estimated available battery energy divided by its estimated kWh required to go one km or one mile and there are several flavors of that latter number. One is the rated consumption and others are based on observed consumption. TeslaFi graphs fully charged range in terms of the rated consumption. If rated range at 80% is 340 km then full rated range should be 425. Be sure you are comparing rated to rated and not rated to average or instantaneous. All these are available on various displays. The latter depend on your driving habits and driving conditions.
You have a new car and it may take a while for your BMS to sort things out. It has quite a difficult job to do in learning the characteristics of your batter and in determining how to manage it.
I think this may be an example of the apples to oranges comparisons I was talking about. The rated range has nothing to do with whether regen is used or not. It is obtained by dividing the car's estimated energy capacity by a fixed number derived from the EPA rating. The displayed Wh/mi is obtained by dividing the watt hours consumed by the distance driven. There are lots of Wh/mi numbers available including instantaneous, 5, 10 or 30 mile averages, since the start of this trip, since the last charge and since the resets of the two trip OD's. Ranges estimated from these can vary all over the place and, of course, regen is counted here. My best Wh/mi reading to date is -146 obtained on a short trip in hilly country. My range based on that is, of course, infinite whatever level my battery is charged to.