The barometric correction curve is used to adjust fueling because of altitude changes based on barometric sensor readings. This is especially useful for Alpha-N setups, but may or may not be useful with Speed Density too, depending on the engine setup.
In the barometric correction curve Y-axis is amount of fuel and X-axis is the barometer reading. 100% means that no correction is applied. Bigger percentage makes mixture riches and lower percentage makes mixture leaner. By default this curve should be 100% at all points, but the correction can be adjusted based on AFR observations at different baro pressures.
