It measures four things: pitch (high squeaky barks usually mean excited, low grumbly ones mean alert),
speed (fast repeated barks mean more worked up), place (which you tap in yourself), and
movement (how much changes on camera between one picture and the next).
The camera cannot tell a tail from a head — a person walking past counts too. It only measures how much is moving.
Then it looks up an answer in a list of rules. It is a guess, not real translation. Nobody can turn
barks into English sentences — but pitch, speed, place and movement really do tell you something.