Calming signals are individual, and a 'snap shot' often misses what other signals go with the photographed head, like tail carriage, body stance, muscle stiffness, movement etc. Calming signals, are body language, that is offered not just when in stress, but all the time. Licking your lips in this house, means yum, food. The anxious lip lick is very rapid, fleeting, and only the tip is used. the lip lick in the pic, is rather large for my dogs distressed lip lick.
You also need to know the context the dog is in, when giving you them. Then the whole picture can be added up to a pretty good accurate guess.