If your Barometer readings do not agree with the local airport or television station, it is because you are looking at two different kinds of readings. “Station pressure” is the true pressure at your site, or station. This is the pressure a mercury barometer would read in your classroom. This is also the pressure that your Vernier Barometer is calibrated to read. “Sea-level pressure” is the pressure after the station pressure has been adjusted to its equivalent at sea level. Airports and television stations usually report the sea-level pressure rather than the station pressure. This is commonly done to take altitude out of the equation for weather forecasters.
If you want your Vernier Barometer to read sea-level pressure instead of station pressure, you can perform a single-point calibration using a reported pressure at your elevation.