The general rule for amplification of any sort is 'input low, output high'. Don't overload the input, keep the main amp full up. That rule obviously needs to be modified when the main amplification is of a size and power un-matched to the room. You CAN practice at home on the PA system you also use for performances in large halls, but you'll want to turn the main volume down!
How does that apply to your digital piano? Well, for a start, there's no 'calibration'. Your piano imitates a real one in many respects, but not to that degree of detail. There isn't a magic volume slider setting that will equate it to a Steinway D or a Kawai upright (to go from the sublime to the, well, less sublime...) And the same setting will sound louder in a minimalist wood-floored room than in one with carpets and soft furnishings.
Set the volume level full. If it's painful (for you or the neighbours) when you play loud, bring it down a bit. But not so much that you find yourself 'hammering' the keys to get a ff.
It is harder to play softly than to play loud. It is also harder to play softly and evenly on a piano that needs regulating (so that every key responds the same). A real piano CAN be regulated. A digital mostly can't, you just have to live with it.
One practical point. Many electric keyboards use rubber strip contacts under the keys. They wear out. Keyboards with weighted keys (as anything pretending to be a 'piano' will have) tend to wear these out quicker than those with unweighted keys. Probably because pianists hit them harder to get 'more tone'. Well, you won't get more tone, just more volume. But if you turn the volume slider fully up, you'll HAVE to hit the keys more gently or risk deafening yourself. So it will be longer before the expense of a keybed overhaul.