OK, this is a straight forward cube to calibrate your 3D printer.
The cube id 20mm3 and you can use it to calibrate the steps per mm for your different axes.
So print the model, once this is done you are able, if your 3D printer allows it, to adjust your Steps per mm in your printers firmware.
e= expected dimension
o = observed dimension
s = current number of steps per mm
(e/o) x s = your new number of steps per mm
In part though this is the result of a guide on how to make your own 3D printer calibration cube using Freecad
So why not have a go at making your own!
Once you master this you will never want for dice ever again!