Fliiiight trainers come calibrated for a standard 700c road wheel or 29" MTB wheel. If you have a different wheel size, update your wheel rim circumference in the 4iiii app for the most accurate power reporting.
Fliiiight does not require a regular re-calibration because there are no extra variables such as mechanical wear and tear or changing tire pressure and rolling resistance influencing its power calculation.
Fliiiight has highly accurate power measurement (+/- 1%). However, if you prefer, you can calibrate Fliiiight to match another powermeter, for consistency between your indoor and outdoor power measurement.