Calculate expression not working correctly.

Hi all,

I'm pretty new to Power BI and DAX functions and I'm having a bit of trouble trying to get one to calculate correctly. I have exam data that grades a learners performance with either a fail, pass, merit or disitinction. I've created 5 columns that works out what the grades would be if the pass mark for each section was reduced by 1 point each time.

When I've tried to count how many distinctions we would have if the pass mark was reduced by 1 point, it's counting other values as well and I'm not sure why. 

Here is my DAX expression:= 

Writing -1 Disitnction = CALCULATE(COUNT('Pass Rates'[Writing -1]),'Pass Rates'[Writing -1]="Distinction")

 

And here is my table, ignoring the last 4 columns you can see I'm getting results for merit and pass even though that isn't in my expression. Any help anyone can offer would be greatly appreciated. : )