Create a calculated field for SUM([Number of records]) label as "Grand Total". Create another calculated field: SUM([LOD Discount])*([Grand Total]), convert to discrete & place on rows shelf next to LOD Discount. Convert Grand Total to discrete and place on rows shelf next to that to keep the grand total row.
Thank you so much for your reply while I think the number is not going to be right after I try. I think it probably cause by using details and aggregation data in the same view ,
My current solution is to create the aggregation in the back end (SQL Database) and align with( join) the original data by the dimension. In this case, the product is the join key. .
Thanks again for your answer!