They are not meant to be an accurate representation of your glucose but an estimate for you to judge what your liver is doing while sleeping, for you to
test upon awakening
in the morning, to
test and provide a baseline measurement preprandial [before meals] level, and to test to see how the foods you consumed affected your glucose level postprandial [2-3 hrs after meal]. Random testing is useless, don't bother as you have nothing to refer against.