You can do it - that's just what most stats are like in that section.
Have a look at the Use of 'SUM' section in this part of the tutorial.
I'll update the tutorial to make it a bit clearer when I have time. It's relatively new, so if you find anything else you don't understand please let me know. Can you give me a link to the specific post where you saw this, thanks.: "HCPS stats are based on the number of times a certain action or event occurred."
