Hello Saifsafwan,
Long story short, the ":" is used to define the general POV of the get-databuffer you want and the other terms separated by "," are the detail you want. Also, the entity dimensin belongs to the data unit so it's better not to mention it explicitly in the calculation.
In the example below, the common members are defined and fixed (O#Top:I#Top:U3#Top:U4#Top), then you ask for the detail you need (U1#ProfitCenter.Base , U2#Location.Base).
Also, during testing you can log the databuffer to know exactly what you're selecting and try to use the "RemoveZeros" function.
Example: FilterMembers(O#Top:I#Top:U3#Top:U4#Top, U1#ProfitCenter.Base , U2#Location.Base).
Regards
