Group By function - ditching extra columns

Hi,
I'm a complete newb I'm afraid, so this may be an over simplistic qusetion, but I have set of data like this:
Col1
a
a
a
b
b
c

And I want to do a group by and count to pass into an HTML Table Viewer. The Group Data By Tag function does what I want, but it produces an extra unwanted column, 'Data', which contains the ungrouped data and is always passed to the HTML Table Viewer. Using Remove Property doesn't work to get rid of this.
My output based on the above example should look like this:
Col1 NumberInGroup
a 3
b 2
c 1

Thanks in advance for any help