meter readings

If they were the finger prick readings (which I'm presuming they are), they are measured in mmol/L in the UK and many other places
Given that you blood sugar levels can change a lot through the day (dependent on lots of things including food eaten, exercise, stress, illness etc) and I imagine not all 3 tests were done at the same time, all would have been as accurate as they can be, as they are snapshots from that exact moment in time.

@Rokaab is correct, it's the mmol/L scale which is used in the UK.
The US uses mg/dl so you multiply by 18.

Either way they are high, how did they treat you & have you come down since ?

If you are in the UK the meter units will be mmol/l . As to which reading is right, probably all of them.
The meters have to conform to the industry standard of plus or minus %15 . If you take the middle reading as the average the other 2 are well within the %15 error margin. It's pretty stressful being in hospital, stress will cause your liver to release some stored glucose into your blood which could explain some of the glucose the meter is reading. However your readings are very high and can't just be cause by a stressful situation