L-M indicate the size of the module and therefore the contact surface, which is important for representing the area to be treated.
720-880-1160 are the numbers that accompany the model letter. They simply correspond to the quantity of kcal removed in 40 minutes (Reminder: 1 kg of fat corresponds to 9,000 kcal).
Concerning Sonical, it is a module containing only one plate for a destocking of 400 kcal in 40 min.