ADXL345 accelorometer: what kind of numbers should i expect tapping sensor?

I hooked up the ADXL326 Analog Sensor, here is some of the data i got while flicking it pretty hard, looks like you can spike 20G's while flicking it. My sample rate is pretty decent too, the code is negligible so it just comes down to the serial print functions being the limiting factor.

It doesn't seem like there is much help on the serial sensors, and a lot of people having similar issues with no resolution. A shame really.