It’s pretty close to that easy. Just create template column that joins the email and the symbol together. Then create a multiple relation column that links the template column to itself. Finally create a rollup column that uses that relation.
That is the foolproof way to do it, but the way you did it with just the symbol will also work because you are currently using row owners. It might not appear that way in the data editor, but the count will only be for one user on the front end because of row owners.