This is a larger cube (50x50x50mm) with smoothed-off edges for calibrating your printer.
The XYZ text debosses are offset to the corners so that their edges won't interfere with your calipers. All the corners and edges are chamfered and filleted so that no corner blobbies interfere with an accurate caliper reading.
If you are trying to dial in your steps per millimeter give it a shot. Printing time is quite long compared to the 20mm standard cube, but it lets you get an accurate reading.
To get the printing time down while still having a nice roof, try a 3d infill pattern with gradual steps (quarter cubic, for example 20%, gradual infill steps at 1)