Totals incorrect for visual level calculation

Hi,TrevLc 
Thank you for your replay
If you have more than one product and are calculating the difference between the current day's and previous day's quantities for each product on a row-by-row basis, and ultimately returning the correct sum of the differences, you can refer to the test I've done below
Here is my test result: 

Versus previous = 
VAR prev=IF([Product]=PREVIOUS([Product]),
[M_Amount_value] - PREVIOUS([M_Amount_value]),
[M_Amount_value])
VAR differ=
SUMX(VALUES([Date]),
CALCULATE(prev)
)
return
IF(ISINSCOPE([Date]),
differ,
[Sum of C_Difference_3]
)

C_Difference_3 = 
VAR CurrentValue=[Amount]
VAR PreviousValue = CALCULATE(
    MAX('Table2'[Amount]),
    FILTER(
        ALL('Table2'),
        'Table2'[Product] = EARLIER('Table2'[Product]) &&
        'Table2'[Date] < EARLIER('Table2'[Date])
    )
)
RETURN

CurrentValue -PreviousValue

Here is  my test data:

I hope my suggestions give you good ideas, if you have any more questions, please clarify in a follow-up reply.

Best Regards,

Carson Jian,

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