I have found the answer. There are 2 different procedures, one is called CONDITIONING and the other is CALIBRATING. Conditioning of a brand new battery involves one cycle of 12 h uninterrupted charging followed by complete drainage of the battery until MacBook shuts down (repeat this 3 times). Calibrating can be done afterwards on old batteries and involves the usual instructions given by many websites (here, Lifewire, Apple, etc).
