This is a read-only property. It is incremented each time that any change is made to any of the features or to any property that would change the way that features are exposed. It is made available so that callers can have a convenient way of knowing if feature-dependent computations need to be flushed from a cache.
The Signature property can be used to detect changes in a particular feature.
The change counter is shared by all McFeatures, so that it will always be unique.