My DD has been placed in Band A after 2nd round of admission test. What does that mean to us? Can I say that she got a place?
I am trying to understand how many candidates are in Band A also.
No, it means - as it says in the email - that in at least one of the last three years your DD would have got a place (but possibly after waiting list, no-one is clear on that).
So, last year, which is where the waiting list went furthest down of the last three years (to the early 140s?), your DD would certainly have got a place (perhaps after waiting list). For the other two years, she would very likely have got a place. If your ranking - which nobody in Band A knows - is between the lowest ranking that got a place in the hardest of the three years and the highest ranking that got one in the easiest of the three years - that leaves you vulnerable.
However, you'd get a better response if you posted in Hertfordshire (North & London) as you've asked this in Essex-Redbridge.
Maybe the mods might move the thread.