Good news! Calibration worked!
The English translated Chinese instruction I got from the seller didn't fully cover it but once you understand, it is very simple.
These are the steps:
1. Get car in calibration mode: start engine until tire pressure display comes on (before this sequence i made sure the tire pressure display was selected). Then shut off. Do this 5 times. On the 6th start, the calibration mode is active.
2. This is what you see in calibration mode: see first picture. To the wheel without dashes: let air out until a yellow coloured pressure is shown. I only had to let out a few tenths of bar.
3. Do the next tire that has no dashes shown (display updates automatically after previous step.
4. Repeat step 3 until no more tires without dashes. I had to repeat the whole sequence due to an error in the Chinese translation and on the 2nd try the last tire was not needed so i only did 3 tires.
The 2nd picture was from my first attempt when i did all 4 tires.
I used 2 phones and a FaceTime video session for convenience so i could see my dash while out of the car (2nd picture is screenshot so bit blurry).
5. Shut off engine and restart. Not sure this was needed but did it anyway.
6. Inflate all tires to 2.5bar on the compressor (car shows 2.4) using the supplied compressor in my 300h. Nifty little device and quite useful.
6. Did the TPMS set (button under steering column.
Happy days!!
I believe this calibration sequence effectively is a TPMS relearn that you can also do with an OBD tool like Autel TS501 or Tire Assistant + dongle (Android only).
For those interested in TPMS and Toyota/Lexus, i found this video insightful ( Car Care Nut).
All you need to know about Tire Pressure Monitor For Toyota