Use of Dummy keyfigures / hidden keyfigures

Hello Experts,

In some of the queries, I have observed that there are dummy keyfigures/ hidden keyfigures (which are greyed out). I tried searching in SCN forums regarding this but could not find a suitable answer.

Can anyone please explain what all scenarios these kind of columns are used in a report.

Plz explain with an example.

Thanks & regards,

Mohammed.