I'd recommend people going through the patent itself rather than relying upon interpretation of it on SEOBook. The way that's phrased could potentially be misleading.
A target rank, which is the rank that a site would move up to from the old rank, based upon the initial changes, is already calculated under the process described in the patent before a page (or site, or group of sites affiliated with each other in some manner) enters into the transition rank function.
The transition rank function period, which would cause the site to either move up more slowly than it normally would, decrease in rank for a period of time before moving up to the target rank, or fluctuate randomly or in unexpected manners before moving up to the target rank.
A page might be "flagged" as in entering into a transition rank stage, but not flagged as in determined by Google to definitely be engaging in Web spam. It's in the possible reactions to a slower than expected rise, or a decrease or random rankings where Google might determine if a person controlling a site might be engaging in Web spam by looking for signs of things like keyword stuffing or invisible or tiny text or misleading redirects, etc.
A page wouldn't "plummet" to a target rank under this patent - the target rank is the rank where the page would rise to from the original old rank.