SSRS Sum in table group

I am working on SSRS reporting services. I have a table on which I applied group. Originally I had this data:

I changed something in my tablix and created a tablix and added a parent group of Age i.e. left column and then in the right column, I applied an expression: =SUM(Fields!AgeTotal.Value, "Group1") which made the result like this:

Now I want 3,3,3 and 2,2 not to repeat and make them 1 row of each group. Like this:

UPDATE:

Right Click on the details cell and select add Total, then right click on the entire details rows and change it's visibility to Hide. This should do the trick!

EDIT

Setp by step tutorial with Image:

First image example: on the left the result you want, on the right the result you get from a simple grouping.
I'm getting the sum(but you could use a count or whatever aggregation you want) of the field lam_larghezza (which, for your information, is a width) group by different lam_spessore values (which, is a thickness)

I'm sorry but mi IDE is in Italian so here a simple translation:

Aggiungi -> Add
Gruppo -> Group
Righe -> Rows
Raggruppa per -> Group By
Totale -> Total
Dividi Celle -> Split Cell
Visibilità Righe -> Row visibility

Let's start!

Create the dataset for the report and clean the report

Add a table to the report

Add the detail field in the data row

Right click on the full row
Add group -> Row group -> father group -> group by grouping field (should be age)

Click on the detail cell (only the cell not the entire row, and remember that the cell had to be highlighted not the text inside the cell, because two different contex menu appear) -> Add Total