You won't see the threshold in 800m. It's unlikely you'll see the first crossbar as it's going to be under the nose of whatever aircraft you're flying so that will leave you with the remaining 4 crossbars, and you may not quite see the 4th, closest to the runway, in 800m vis.
That's as I was taught joining airlines and going on to jets many moons ago, and still practice it successfully. You don't have to "count", as such, the recognition that you have the vis or not is instantaneous aided by the number of bars you see.
It's simply a matter of KNOWING what you need to see at the DA respectively for 800m, 1200m or 1500m requirements which others have already been mentioned in previous post.
In a way I think that was what MyName etc was trying to say .........