First Print with the Simple - 3D Printing: Build your Own 3D Printer and Print your own 3D Objects - page 91

Figure 5.11 Nozzle now in proper starting location.
Manually moving the nozzle isn't difficult, but there is a better solution that
doesn't require you to adjust the three axes by hand. Change back to the Print
Panel shown in Figure 5.12 and note that X, Y, and Z axes each have a collection
of strange buttons with values on them: -100, -10, -1, -0.1, 0.1, 1, 10, and 100.
These values are in mm, and a single click on one of the axis buttons will cause
that motor to move either the print bed or the nozzle that distance.