Looks like I have the same problem as well. My 90% is down to 265. It's dropped from 279 to 265 in the last 3K miles.
Did a trip, charged to 100% which was 295miles! from about 15%. at the weekend. Lost another 3 range after that.
That works out at 5% drop over the last 3K miles. P3D as well, in which case I would be down another 15% by the time the 'annual' service comes around, which definitely doesn't seem right.
My understanding is that the mileage on the main display is the rated miles based on the state of the battery, rather than an estimate based on your driving?
Have booked another service appointment for them to look at it.