To understand that counting on from the larger number works, you have to be completely sure that addition is commutative (1+50 = 50+1).
What I meant was, she doesn't get "counting on" even from the first number. So if I give her 9+2, she can
count all the way up to 9 verbally without losing track of the 2 (which would tax most adults' verbal working memory, if we didn't have our addition facts memorized), but if I suggest that she just start by saying "nine," since she already knows that there are nine, it just doesn't make any sense to her.
IOW, she hasn't yet made the transition from "counting all" to "counting on". She doesn't "really" get that when you count, the ordinal number you used to label the last item is always the cardinal number of the set of items you've counted so far. Which is entirely developmentally normal, but I know how weird it can be to catch our children being developmentally normal from time to time :-)
I have a note of my astonishment at finding that the concept of "more" really did develop in stages in DS, then 3y0m. To casual observation he appeared to understand it, but on reading about how it developed and testing him I found that, indeed, although he could correctly answer "which is more?" questions if both numbers were 6 or less, *or* if they were separated by more than about 10, he couldn't answer "which is more, 6 or 7?". It still astonishes me now, actually - I had a real "how can he not understand that, given all the things he does understand?" feeling about it, but I also had it written down that being able to do this but not that was normal...
