KF aggregation/exception aggregation options

Hi

There is one KF that has defined as

1)aggregation option SUM ,

2) Exception aggregation option Last Value

3) aggregation Ref char 0CALDAY.

4)cumulative value radio button s option is on in Cumulative/Noncumulative values option.

These options can be found in KF declaration in the second Tab.

I understand that from the query point of the KF will display last value/given calday. What is the use of aggregation option SUM (option 1 above)? can you give me one example please.

also one more question what is the use of Ncum Value with Ncum Value change?

Thanks

Vennela