I have this data
DateRecived JObNumber REcCnt
20130626 1234 1
20130627 1238 11
20130628
Here's a small example with some mock data that should be more or less analogous to your situation.
The dataset:
Market SubMarket
------ ---------
A 1
A 2
A 3
B 4
B 5
B 6
B 7
Here are the steps I've taken to create the table:
1) Drag/drop a new, fresh table to the designer.
2) Drag/drop the SubMarket field to the first column.
3) Right-click the detail row and add a new parent group.
4) Group on Market and choose to add a group header row.
As you've already noted, SSRS "helps" and adds an extra column.
5) Right-click the extra (first) column and delete it.
6) Select the cell in the header row for the group and enter "[Market]", or pick it from the quick-list.
7) Finish up by filling in the other fields/columns/cells. For the header row drag/drop won't work, you'll have to pick the fields for that row yourself (or type 'em).
This is the resulting table in preview (with some emphasis on the header row):
For your solution you have to add all the other rows in detail section other than the fields on which you want to apply the group by.