Grinder calibration
Adjusting a grinder so its settings line up correctly with the grind sizes you want.
Calibration sets the point where the burrs just touch (zero) so the numbered settings are meaningful and you can return to a known grind. Some grinders allow you to reset this if espresso settings drift off the dial.
It is usually a one-off or occasional task rather than a daily one.
Why it matters for small spaces
Knowing a grinder can be calibrated helps if your espresso setting ends up at the very edge of the range.