Bg Readings.....

Lots of reasons.
Meters are only required to be accurate to within 15% 95% of the time.
Capillary blood in our fingers moves and therefore changes rapidly.
Rogue strips (happens to us all from time to time)
Human error (contaminated fingers, damp hands etc)

It is normal, and more likely to happen than 2 identical consecutive readings.

I know my left hand is less sweet than my right, no idea why