servicio is the service charge, and in all restaurants these tips are automatically included in the total as an extra 10% - tipping is not mandatory, however it is expected and unless the service was particularly bad, a 10% tip is normal. 

this 10% cannot be applied to the couvert artistico, and it is always clearly marked on the bill - charges above 10% are considered excessive and, again, not mandatory, but are definetely a nice gesture towards good service provided to the clients.