You Can simply Right Click Formula Fields- > new Give it a name like TotalCount then Right this code:
if(isnull(sum(count({YOURCOLUMN})))) then
0
else
(sum(count({YOURCOLUMN})))
and Save then Drag and drop TotalCount this field in header/footer.
After you open the "count" bracket you can drop your column there from the above section.See the example in the Picture