"Actual Size" in Adobe Creative Suite

[Stroller]

In Adobe Creative Suite, I have my artwork set to "View" at "Actual 
Size". When I measure it on the screen with a ruler, I find that it's 
about 75% of actual size. Is there a way to tell either my Mac or Adobe 
what size my monitor is, so that it'll actually damn display 
correctly..?

I could, of course, fiddle with View at 125%, 128%, 132% or whatever 
until I get it right, but that's annoying - I really shouldn't have to 
do that.

Stroller.