Do people find meters can vary in readings a lot? Did a light workout and got a reading of 172 (9.6) after (down from 183 not long before). An hour later, a bit before lunch - 137(7.6). I was shocked so did a second reading right then. 144 (8.0). Is this deviation common?
Meters are required to be accurate to within +/- 15% of the actual reading.
So if your reading is actually 10mmol (approx 180 in your units), then the meter is considered to be accurate enough if it shows somewhere between 8.5mmol and 11.5mmol/l ( 153-207 your units)
Not ideal, I am sure you agree. But realistically, most readings should be roughly in the centre, and therefore more accurate.
Unfortunately, there will always be the odd rogue reading, due to the odd rogue strip, but if you get any reading that just seems too wacky, just wash hands and retest.