What I do is when I come to the 'barely changed' level, I shake it around a lot..and if it doesn't show to a clear color change, add one more drop. If its clearly changed with that one more drop, my notes will show the halfway point. So if 9 was 'sorta changed' and 10 was clearly changed, I put 9.5.
But you should not need the GH/KH testing, just ammonia, nitrite and nitrate.