Calculation happening at non-leaf level also

In my scenario ,calculation should happen only at the leaf level. But the calculation happened at the non-leaf level also in Mondrian.
The values for ‘Sales Amount’ column for Month Level is incorrect as shown above in the 2 nd image with red box.
But the ‘Sales Amount’ value for month level should be ‘18’ as shown above in the 1st image with green box.

Instead of rolling up the ‘Sales Amount’ values of ‘1-july’ and ‘2-july’ , it takes the rollup values of ‘Order Qty’ and ‘Unit price’ in ‘July’ and multiplied those values and assigned to ‘Sales Amount’ in ‘July’.
It should be (6 + 12 =18), but not (9 * 4 = 36)