As mentioned earlier in the thread, BM meters do have a high tolerance for readings.
I noticed that readings can be all over the place, even after testing 3 times in quick succession even on the same meter.
At first, I though my meter was faulty, but the same experience was had with a number of different meters from a couple of manufacturers.
What I also found was that the amount of blood I tested with. For example, if I had trouble drawing blood, and could only barely squeeze enough out to complete the test, this would give me a much lower reading than if ample blood was flowing from my (now sore) fingers.
Essentially, all meters have a tollerace of between 10% and 30%. If you suspect an odd reading, re-take it if testing strip supplies permit.