Real world range is probably based on your last 10 or 25 miles of driving. You can see that in the power graph menu in the car too. You probably accelerated hard, or went fast on the highway, had headwind, went up hills etc... I suggest you read some of the threads around here, discussed plenty.
If you have been driving your new Performance Model Y like you stole it then yes, your range will be lower than expected. Try a few highway runs at something closer to a steady 70 MPH and your estimated range will improve.
Range is always a fun question! Let’s start with the eMPG range, which Is based on the car driving on a prescribed track and in a prescribed manner. Practically no one drives like that! Thinking back to an ICE car, if the MPG was say 30 and you typically got 27 MPG, than you were getting 10% less. Now let’s assume the eMPG on a car is 300 miles, taking that same 10% away means your “real world” range in 270 miles. Next, this range assume 100% battery utilization, typically we use just 60% (80% charge, 20% miniumum) which gives us a “practical” range of 162 miles.
If you are going to base range on what an app tells you, such as TezLab, as @GtiMart noted, you need to understand how it works.