Contains the value of an NSAnimationProgress as an NSNumber instance that indicates the current animation progress. The value will be between 0.0 and 1.0.
Available in Mac OS X v10.4 and later.
Declaration Syntax Version Information- Available in Monobjc Bridge: 10.6 (For Mac OS X 10.6 and later), 10.5 (For Mac OS X 10.5 and later)