It sounds as if the admission number is 130 (5 classes of 30), and 2 extra pupils were originally admitted on appeal. This means the school had no choice in the matter, and I assume the appeal panel took the view that the parents' cases were so strong that they outweighed the prejudice to the school. (The are other possible reasons for an extra pupil such as a statement naming the school, but again, this doesn't necessarily mean there was no prejudice to the school.)
You could try asking at stage 1 what evidence there is that the school hasn't coped successfully with the extra pupils, but your best hope of winning is to focus on your own daughter and explain why it is so important for her to have a place at this particular school.
You ought to start by studying the Q&As:http://www.elevenplusexams.co.uk/11plus ... nswers.php
See, in particular:http://www.elevenplusexams.co.uk/11plus ... ers.php#c2
Technically there is no vacancy at the school until the number drops below 130. In other words, two more children would have to leave before a place becomes available from the waiting list. Your aim should be to convince an appeal panel that your daughter's need for a place will outweigh any prejudice to the school.