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.