I'm usually only actually "remembering" the first 3 or 4, but I'm blaming that on lack of sleep.
When they're clustered tight I have no problem, it's scanning the screen that's the issue.
Ok, not much of a response to this. Anyway, my "trick": I stare at the screen (duh), and as soon as the numbers show up, I shut my eyes quickly (and keep them shut) before they disappear. This seems to retain a fading image (think burn-in), for me, that I can still kinda see while my eyes are closed. If I don't do this, I don't think I could get 10/10. If the numbers are clustered closely together, I can see more of them in the brief moment they're displayed. If they are clustered far apart, my eyes can't see all the numbers clearly without moving at least a little bit, and there just isn't enough time to move your eyes from the initial light exposure before the numbers disappear.
This is on a CRT, and I realize most people use LCDs these days. I'm not sure if this "trick" wouldn't work as well, or at least differently on an LCD because of the different type of light source.