GPAs are funny business. Folks seem to think that they are super important in applications when, really, depending on the region/culture they're not all that important. Sure you have to make a minimum requirement for many jobs(typically a low B in my field but every field is different) but GPA especially at a graduate level is way over emphasized by many students. In the US, far more important than a numeric value is any achievements, activities, actual work you did.
Why do I bring this up if you're not asking about it? A resume should POP. It should be fast to read, get the stuff that's most important to you/your field out and open and, most importantly, hit any important key words so that HR folks pass it on to the 'interview' pile.
Well ok, duh Nahkki. Right?
My point in this is that GPA should be fast, easily digestible and should NEVER EVER take away from the more valuable portions of your resume. "I got an A and this was the best!" Doesn't read well. It's laden with subcontext even though it may seem straight forward.
You say you 'averaged' an A. Which says that at some level there's a numeric system underlying your GPA. GPA, Grade Point Average, that's pretty much how that works. So you should have a 3.8/4.0 (ow whatever) If you're using a 4.0 scale. This should be reported in the same way you report your 8.5/10.0 .
If, for some reason, your school does not calculate GPA in this way then you can easily calculate your own GPA using the marks you received during your MSc.
Honestly, and this is the US in the field of Computer Science, if I saw that someone said they got an 'A' for their MSc I would be a bit weirded out. That's almost certainly different in different countries and different fields. If that's the case I would recommend editing your question to be a bit more specific to the region/field.