Power pivot with measure using measure for subtotal instead or doing total of top rows.

[Mohammed1008]

	2020	2020	2020	2019	2019	2019	2019
	SALES	QTY	Unit Sales	SALES	QTY	Unit Sales	Effect
A	100	10	10	50	4	12.5	25
B	20	5	4				-20
C				10	2	5	0
Total	120	15	8	60	6	10	30

The effect is a column with measure: Sales2020 - (Unitsales 2019 * Qty 2020)

Total Effect should be 5 but it's using the measure formula to populate.

[#2]

@Mohammed1008 

Perhaps you may clarify if not with file but al least by screenshot?

Do we speak about Power Pivot (as in title) and calculated column {Effect} added to the table in it. Or you added the measure, when how column is formed?

Or we speak about Matrix visual in Power BI built on related table?

In any case, Grand Total is not necessary sum of subtotals. Grand Total, in general,  aggregates all data independently on how they are grouped.