Each type key decision factor that you have identified will typically fall into one of these patterns:
Each case has exactly one instance of this key decision factor, e.g. a "total household income" key decision factor for the case;
Each case has a number of instances of this key decision factor, depending on the case's circumstances, e.g. a "total person income" key decision factor for each of the people in the case's household.
Note that the Engine does not impose these single/multiple key decision factor patterns; the creation of key decision factors can be as complex as your business requirements dictate.
For a single key decision factor, the description of the factor can be a fixed piece of (localized) text, e.g. "Total Household Income".
For a multiple key decision factor, each instance of the factor in a determination must have a unique name - this uniqueness is required by the Engine and also is necessary for the case worker to distinguish between multiple instances of the key decision factor. Thus the description for a multiple key decision factor typically requires a calculation involving some fixed text and some variable data from the case, e.g. "Total Person Income for <person-full-name>". Your analysis should include the calculation requirements for these kinds of descriptions.