The meter can be calibrated to take into account filters e.g. +1.6 (varies for each filter). Baseline calibration is with ISO 1 and ISO 2 buttons pressed simultaneously.

The meter does not require any additional calibration on the premise of making sure the exposure is correct that is your responsibility, gained through active experience using the meter.

I would ignore most online commentary regarding the Sekonic baseline mid-tone calibration: it is not particularly well-informed.