Scale has two distinct, sometimes contradictory meanings in die-cast minatures.
Originally, scale indicated a ratio of how large a model was in realtion to its prototype. If a model of a truck was 9 inches long, and the real truck was 90 inches long, then the ratio between the model and the actual truck was 1:10, and the scale was 1:10, also written as 1/10. A model car with a scale of 1:80 was 1/80th as large as the real car. In theory, this size ratio applied not only to the size of the model, but also to the size of all of its parts, so the windshield was 1/80th the size of the windshield on the real car, the model's doors were 1/80th the size of the real doors, etc; however these measurements were often varied as the the model was designed.
In die-cast cars, scale has taken on an additional meaning, often at odds with its original meaning. In die-cast, 1:64 scale has come to mean models that are approximately one inch wide and two or three inches long, reagardless of their size relative to their prototypes. Thus the Faun Quarry Dump Truck, the Alfa Romeo Giulia Sprint GTA, and the Land Rover Defender, all of which are about one inch wide and two or three inches long, are all considered 1/64 scale, in spite of the size ratio for the dump truck being 1/140, for the Alfa being 1/59, and for the Land Rover being truly 1/64.