You can make key decision factor information available for a determination by creating a custom KeyDecisionFactor rule set and associating this with the product. Your custom rule set should extend the DefaultProductKeyDataRuleSet.DefaultCase class and provide a derivation for the keyDataTimelines attribute. This attribute is responsible for collating the key decision factor information that gets displayed on the screen.
The keyDataTimelines attribute returns a list of 'AbstractKeyDataTimeline' rule classes. Each AbstractKeyDataTimeline class is considered a separate category and can choose to implement the 'timeline' attribute, the 'keyEvents' attribute, or both.
These attributes allow for two distinct type of key decision factor, the key events are displayed as a date on which an important event occurred, i.e. "<event> on <date>", e.g. "Robert Smith turned 18 on 10/10/2011". The timeline attributes are displayed as a series of changes, i.e. "Changed from <old value> to <new value> on <date>", e.g., "Total household income changed from 100 to 150 on 10/10/2011".
For our simple product, the amountTimeline attribute in the eligibility and entitlement rule set could be referenced as a key decision factor 'timeline' attribute to allow a user see, at a glance, the changes to the amount over time.