The Power Smoothing function in the SYSTM app will give a rolling 3-second average power on the screen, rather than reporting instant power from your power source. The numbers you see on the screen will have less fluctuation. The app will record the actual data, not the smoothed data, so the graphs will still show the natural power fluctuations.
You can turn Power Smoothing ON or OFF with the toggle found on the SETTINGS screen in the workout player settings panel. Click on the gear in the top right corner of the workout player screen to access this panel.