You zero for point-of-aim and point-of-impact to coincide at 1K meters.
Any effect microgravity would have on the path of the bullet would be minimal, and would vary based on the shooter's orientation at the time was shot was fired, so it's not worth considering.
That's my guess.
ETA: This assumes the availability to zero in the same environment as the weapon would be used.To zero on earth, you'd need a target that accounted for gravity and height over bore.