Days computation

Hi mussaenda ，

You could try the following steps，let first output:

You could use the following measures:

end = 
VAR end1 =
    CALCULATE (
        MAX ( 'Table'[LOADING DATE] ),
        FILTER ( ALL ( 'Table' ), 'Table'[MATERIAL] = MAX ( 'Table'[MATERIAL] ) )
    )
VAR end2 =
    IF ( end1 <> BLANK (), end1, TODAY () )
VAR test1 =
    DATEDIFF ( MAX ( 'Table'[OFFLOADING DATE] ), end2, DAY )
RETURN
    test1

Then the secend output：

You could try the following steps:

Step1, create start_dt and end_dt,base on base table :

start_dt = FORMAT(MAX('Table'[OFFLOADING DATE]),"YYYY/MM/DD")

end_DATE1 = 
VAR end1 =
    CALCULATE (
        MAX ( 'Table'[LOADING DATE] ),
        FILTER ( ALL ( 'Table' ), 'Table'[MATERIAL] = MAX ( 'Table'[MATERIAL] ) )
    )
VAR end2 =
    IF ( end1 <> BLANK (), end1, TODAY () )

RETURN
    end2

then get just as following:

And then use the following measures:

January：

onemon =
VAR test1 =
    IF (
        'Table'[start_dt] >= FORMAT ( "2021/01/01", "YYYY/MM/DD" )
            && 'Table'[start_dt] <= FORMAT ( "2021/01/31", "YYYY/MM/DD" )
            && 'Table'[start_dt] <> BLANK (),
        IF (
            FORMAT ( [end_DATE1], "YYYY/MM/DD" ) <= FORMAT ( "2021/01/31", "YYYY/MM/DD" ),
            DATEDIFF ( MAX ( 'Table'[OFFLOADING DATE] ), [end_DATE1], DAY ) + 1,
            DATEDIFF ( MAX ( 'Table'[OFFLOADING DATE] ), "2021/1/31", DAY ) + 1
        ),
        IF (
            'Table'[start_dt] <= FORMAT ( "2021/01/01", "YYYY/MM/DD" )
                && 'Table'[start_dt] <> BLANK (),
            IF (
                FORMAT ( [end_DATE1], "YYYY/MM/DD" ) <= FORMAT ( "2021/01/31", "YYYY/MM/DD" ),
                DATEDIFF ( "2021/01/01", [end_DATE1], DAY ) + 1,
                DATEDIFF ( "2021/01/01", "2021/1/31", DAY ) + 1
            ),
            0
        )
    )
RETURN
    test1

Jan = IF(HASONEVALUE('Table'[MATERIAL]),[onemon], SUMX(ALL('Table'),'Table'[onemon]))

February：

twomon =
VAR test1 =
    IF (
        'Table'[start_dt] >= FORMAT ( "2021/02/01", "YYYY/MM/DD" )
            && 'Table'[start_dt] <= FORMAT ( "2021/02/28", "YYYY/MM/DD" )
            && 'Table'[start_dt] <> BLANK (),
        IF (
            FORMAT ( [end_DATE1], "YYYY/MM/DD" ) <= FORMAT ( "2021/02/28", "YYYY/MM/DD" ),
            DATEDIFF ( MAX ( 'Table'[OFFLOADING DATE] ), [end_DATE1], DAY ) + 1,
            DATEDIFF ( MAX ( 'Table'[OFFLOADING DATE] ), "2021/02/28", DAY ) + 1
        ),
        IF (
            'Table'[start_dt] <= FORMAT ( "2021/02/01", "YYYY/MM/DD" )
                && 'Table'[start_dt] <> BLANK (),
            IF (
                FORMAT ( [end_DATE1], "YYYY/MM/DD" ) <= FORMAT ( "2021/02/28", "YYYY/MM/DD" ),
                DATEDIFF ( "2021/02/01", [end_DATE1], DAY ) + 1,
                DATEDIFF ( "2021/02/01", "2021/02/28", DAY ) + 1
            ),
            0
        )
    )
RETURN
    test1

Feb = IF(HASONEVALUE('Table'[MATERIAL]),[twomon], SUMX(ALL('Table'),'Table'[twomon]))

March ：

threemon = 
 VAR test1 =
    IF (
       'Table'[start_dt]>= FORMAT("2021/03/01","YYYY/MM/DD")
            &&'Table'[start_dt]<=  FORMAT("2021/03/31","YYYY/MM/DD")
            && 'Table'[start_dt] <> BLANK (),
        IF (
            FORMAT([end_DATE1],"YYYY/MM/DD") <=FORMAT("2021/03/31","YYYY/MM/DD"),
            DATEDIFF ( MAX ( 'Table'[OFFLOADING DATE] ), [end_DATE1], DAY )+1,
            DATEDIFF ( MAX ( 'Table'[OFFLOADING DATE] ), "2021/03/31", DAY )+1
        ),
        IF('Table'[start_dt]<=FORMAT("2021/03/01","YYYY/MM/DD") && 'Table'[start_dt] <> BLANK (),IF (
            FORMAT([end_DATE1],"YYYY/MM/DD") <=FORMAT("2021/03/31","YYYY/MM/DD"),
            DATEDIFF ("2021/03/01", [end_DATE1], DAY )+1,
            DATEDIFF ( "2021/03/01", "2021/03/31", DAY )+1
        ),0)
    )
RETURN
   test1

Mar = IF(HASONEVALUE('Table'[MATERIAL]),[threemon], SUMX(ALL('Table'),'Table'[threemon]))

April ：

formonth = 
 VAR test1 =
    IF (
       'Table'[start_dt]>= FORMAT("2021/04/01","YYYY/MM/DD")
            &&'Table'[start_dt]<=  FORMAT("2021/04/30","YYYY/MM/DD")
            && 'Table'[start_dt] <> BLANK (),
        IF (
            FORMAT([end_DATE1],"YYYY/MM/DD") <=FORMAT("2021/04/30","YYYY/MM/DD"),
            DATEDIFF ( MAX ( 'Table'[OFFLOADING DATE] ), [end_DATE1], DAY )+1,
            DATEDIFF ( MAX ( 'Table'[OFFLOADING DATE] ), "2021/04/30", DAY )+1
        ),
        IF('Table'[start_dt]<=FORMAT("2021/04/01","YYYY/MM/DD") && 'Table'[start_dt] <> BLANK (),IF (
            FORMAT([end_DATE1],"YYYY/MM/DD") <=FORMAT("2021/04/30","YYYY/MM/DD"),if(FORMAT([end_DATE1],"YYYY/MM/DD") <FORMAT("2021/04/01","YYYY/MM/DD"),0,
            DATEDIFF ("2021/04/01", [end_DATE1], DAY )+1),
            DATEDIFF ( "2021/04/01", "2021/04/30", DAY )+1
        ),  0)
    )
RETURN
   test1

Apr = IF(HASONEVALUE('Table'[MATERIAL]),[formonth], SUMX(ALL('Table'),'Table'[formonth]))

Click follow to download pbix file if you need!

Wish it is helpful for you!

Best Regards

Lucien