2020 Prime ... EV only = 16 miles

What your asking is immaterial - EV distance is highly suspectable to how aggressive you drive, weather, and terrain conditions. One thing you can count on is it's going to get worse as it gets colder. Rather than using DTE as a gauge, switch over to the miles per KwH usage table for a better indication of your driving habits and go from there. I believe that table will go back two months and will give you daily averages, so you can vary your driving behavior over the same commute route to determine your best results.

Hope this helps...

 

@Moe_b what @BiomedO1 explained above ^ is a good way to start understanding why you are only getting around 16 EV miles per full charge. ( I hope I'm reading your posts correctly ).
There is a limit to how well the EV will preform in the old Gen 3 Plugin Prius as well as the Gen 4 and Gen 5 Primes (mostly due to their smallish battery packs).
Simply, the slower an owner drives in EV mode the more EV miles they can get. Like @BiomedO1 explained above, there are other variables that effect EV miles in the Prime like wind direction and headwind speed. temperature, ( as soon as the temps drop below 60 F ( all day long ), expect the EV miles to start to decline.
The speed driving in EV mode is the big one though for a couple of reasons.

At 161K miles it's not going to be easy to recover due to the Primes history data saved in the main ECU ( where I believe the car keeps track of the cars history data, error codes, engine, motor and sensor parameters).
.
But, it you are determined and have (patience) it can be done over time, slowly.
Use HV mode more at higher speeds and use ( EV mode when available ) at lower speeds and especially down big long hills at the slowest speeds traffic allows.

( it takes training to go slower, (( even ) the Go Pedal foot ) typically habitually pushes the Go Pedal down. The leg and ankle muscles need to be exercised to back off the Go Pedal. It's not a natural driving experience to slow down these days.

Importantly ( it's not that you have to always practice slowing down ) not in today's typical scenarios, but whenever you can practice without interfering with other traffic that's the time to practice when you (( remember )) too and even at 161 k miles you might be able to see your EV miles increase during warm weather and lighter traffic times !!