When reducing/combining duplicated rows by multiple reference columns with numeric values, the 2nd reference column and on were calculated,

E.g. With following data,

1. Choose Worksheet: Reduce/Combine Duplicated Rows

2. Choose 1st two columns as reference columns.

3. Set Merge Duplication by Sum.

4. ==> After clicking OK, the 2nd reference column set were not kept, instead, it was added up.