I only ever see 100% 32 miles after a full charge unlike the ZS which varied depending on GOM interpretation of history.
When the car / battery is brand new, this is completely normal.
If it is anything like the VW PHEV that I owned for over four years, you will see after about 12 months that predicted figure will start to fluctuate slightly after a full charge.
Dependant on weather conditions etc, you will see it start to produce a slightly smaller range on the GOM after a full charge.
This was a common feature that other owners had also witnessed as the pack ages slightly.
First year from brand new, it report the max 31 - 30 miles of predicted range on the GOM.
In the second year it started to report slightly less after the same full charge of around 30 - 29 miles.
Third year about 29 - 28 miles.
These are ALL figures reported in the summer time.
I kept a log of this actually happening, it happened almost at the same point every year !.
The winter reported figures where slightly less of course !.
Lithium Ion packs tend to degrade more quickly in the first 12 months, then the subsequent following months.
The manufactures known this and under report the spec slightly to accommodate the fact.
You COULD keep a record of your ACTUAL mileage covered ( not the predicted range ) and check any decline in range this way.
But to be honest, I would not even bother !.
If the MG PHEV is in any way related to the VW set up ( and there is clear evidence that the VAG parts bin has been heavier raided for the ZS EV ) then I would expect the MG PHEV to react in the same manner, given time.
Just to say, this lower reported range can be a little disconcerting when / if you come to witness it for the first time !.
But it had become an accepted fact with VW GTE owners.
The theory was this in the end :-
“Just charge, drive and enjoy the car”.
Life is too short to be worrying what the GOM reports you SHOULD receive in range.
It is called a GOM for a very good reason.
Remember the figure is just a prediction and not an actual true fact.
It’s guess ( although sometimes fairly actuator ) is purely based on a LOT of fir rent factors, like weather, driving style and so on and so forth !.
It’s much less important in a PHEV because you have a HUGE back up supply of fuel being carried around in the fuel tank.
Use the electric energy to suit the conditions of the trip.
If the journey is short and of lower speeds, use electric ALL of the time.
If the trip is of a longer nature, choose how and when you consume your EV range.
For longer stretches of the journey at higher speeds, then pure electric mode will eat the energy real fast !.
Save the electric range for slower sections and for town work etc.
Does the MG PHEV have a “Hybrid Auto” function ?.
If so, let that judge what it needs on higher speed sections of the trip.
I found the VW PHEV extremely economical and reported anything from 90 -110 MPG.
By the ZS EV beats it hands down for economy.
Enjoy ?!