Scale is short for Quantification-Scale. The Quantification-Scale describes a dimension of "how well", which is critical to avoid failure and/or can ensure success in the project. The Stakeholder-Values and Product-Values are expressed through the Quantification-Scale.
It is crucial to find and specify the critical Stakeholder-Values and Product-Values, and to find out how to Quantify them as directly as possible in the Quantification-Scale. The Quantification-Scale is the heart of Stakeholder-Value and Product-Value Specifications. Stakeholders should agree that improvements along the Quantification-Scale are exactly what they want from the project, that improvements along the Scale will make them dance in the street and that they would love to pay for it, otherwise we probably will improve in the wrong direction.
The Scale contains a Unit-of-Measure, a Rate and a description of its Context. In a Scale, the Unit-of-Measure is left open (empty), as in "average time in minutes" without entering a specific number. This way we can reuse the Scale without rewriting it for each point along the Quantification-Scale.
We never use more than one Scale per Stakeholder-Value or Product-Value statement. When we need several Scales to express a Stakeholder-Value or Product-Value, we break them up and create a new Stakeholder-Value or Product-Value for each Scale with its own Name, and its own set of Parameters (Past, Goal etc.)
Scale defines the 'how well' and should not be confused with how we Measure. We will call the how we Measure a Meter, as in speedoMeter.
Illustration: the arrows are symbolic of the Scales. From left to right is symbolic of from worse to better.