They indicate fractions of a second. The larger the number the shorter the exposure. This is fast enough to stop someone riding a bicycle. The third control is the film speed setting. Some films react to light more rapidly than others.
Every film has a speed rating on the box.
There used to be ASA ratings, and now there are ISO ratings. The numbers haven't changed. The film speed is set when the roll of film is placed in the camera, either manually or automatically depending upon the camera. The other controls can be varied with each shot, but usually the film is set at its proper speed and left that way. One might focus on someone twenty feet away.