Want to create a Measure, Value want to insert in Rows under category

DeepakSharma_01 
You can achieve the solution by using a Disconnected table and measures. Below is the code and steps.
Steps 1 :
Create a disconnected calculated table using below code

DisconnectedTable = 
VAR _1 = 
ADDCOLUMNS(
SUMMARIZE( 'Table','Table'[Region],'Table'[REV_REDUCTION_TYPE] ),
"Sort",RANKX( 'Table',[REV_REDUCTION_TYPE],,ASC )
)
VAR _HighestSort = 
ROW( "check",
MAXX(
    _1,[Sort]
) )
VAR _2 = 
ROW( "Region","Africa","REV_REDUCTION_TYPE","Off_invoice","Sort",_HighestSort +1)
VAR _Result = 
UNION(
    _1,_2 
)
RETURN
_Result

Step2 : Create below measures

Net Amount = 
VAR _NM = 
CALCULATE(
    SUM( 'Table'[Net Amount] ),
    TREATAS( VALUES( DisconnectedTable[REV_REDUCTION_TYPE] ), 'Table'[REV_REDUCTION_TYPE] ),
    TREATAS( VALUES( DisconnectedTable[Region] ), 'Table'[Region] )
)
VAR _BGM = 
SUMX(
   FILTER( 'Table', 'Table'[REV_REDUCTION_TYPE] = BLANK() ),
   [Gross Amount]
)
VAR _BNM = 
SUMX(
   FILTER( 'Table', 'Table'[REV_REDUCTION_TYPE] = BLANK() ),
   [Net Amount]
)
VAR _Diff = 
_BGM - _BNM
VAR _Result = 
IF(
    MAX( DisconnectedTable[REV_REDUCTION_TYPE] ) = "Off_invoice",
    _Diff,_NM
)
RETURN
_Result

Gross Amount = 
VAR _GA = 
CALCULATE(
    SUM( 'Table'[Gross Amount] ),
    TREATAS( VALUES( DisconnectedTable[REV_REDUCTION_TYPE] ), 'Table'[REV_REDUCTION_TYPE] ),
    TREATAS( VALUES( DisconnectedTable[Region] ), 'Table'[Region] )
)
VAR _Diff =
IF(
    ISBLANK( [Net Amount] ), BLANK(),
    0 )
VAR _Result = 
IF(
    MAX( DisconnectedTable[REV_REDUCTION_TYPE] ) = "Off_invoice",
    _Diff,_GA
)
RETURN
_Result

below screenshot

 i have test this without blank reduction type as well

Attached pbix file.

Hope it will help.

Regards

sanalytics