The way it's implemented seems to negate the smoothing issues due to high polling rates, at least below 1000 Hz.
The "Mouse Sensitivity" value will default to 0.5, the other two values, X and Y-Axis Sensitivity are the ones that are calculated.
If you get a very high discrepancy you can try to adjust the "Mouse Sensitivity" value manually to get the discrepancy lower. Adjust it in steps of 0.05 so you can match it in-game.