I am trying not to get overly concerned with results like this, my meter is +/- 15% accurate which i dont think is abnormal. I think you might be able to get +/-10%.
However, a result say -5% first, and then a +5% result can give a large degree of difference. To the full range it can be 20% or 30% different if the full range of inaccuracy plays out in opposite directions on the two tests. 5.0 to 6.0 between tests could be 5.5 consistently with a +/-10% accuracy
Best not to get overly concerned about it really, use it as a guide to help inform your choices and allow the HBA1C test be your main measure.