Last Function in Report returns #MULTIVALUE

Hi Everyone!

I have a report in which I am trying to retrieve the last value of a variable.  The variable I am trying to get the last value of is defined as a detail.

Here is how I am trying to retrieve it:

Variable is defined as measure:  Last([Chart Data]) In Report

When I drag this out to the report by itself....it returns #MULTIVALUE.

Any ideas as to why this is happening?  Does it have to do something with it being performed on a variable that is defined as a detail?

All and any help is greatly appreciated!!

Thanks!!!