The data you have posted is not the same as you quoted in earlier posts.
From the data above this says that
Current reception has a PAN of 45 and they have 47 in it, so 23/ 24 in classes
Current year 1 has a PAN of 45 and they have 47 in it, so 23/24 in it
Current year 2 has a PAN of 60 and they have 51 in it., so classes of 25/26
On that basis if the appeal is for reception year the classes are no where near the 30 maximum and the same for year 1. In year 2 there are currently 51 and in theory this could increase to 60 as per the PAN and up to that point the school must admit. If they got to 60 this year and there was an appeal this year for a year 2 place then this appeal would be an infant class size case.
However if you assume (which you must) that the PAN is going to stay at 45 and assume (which you must) that the school is going to have two classes in reception, year 1 and year 2 then no appeal can be an infant class size appeal because no year group can exceed 30 in a class without significantly exceeding its PAN.
For the school to argue infant class size appeal then they would have to show that they only have 5 class rooms available. This would then mean that longer term they are going to have 2 reception classes of 22/23 and three year 1 /2 classes of 30. But they simply can't do that when they currently have 6 classes and are using all 6 classes. They would have to provide a very, very good reason to show that they reducing to 5 classes.
The fact that there have been successfully appeals for both reception and year 1 prove that their current system has been in place for at least 2 years and that appeal panels have not been convinced of the prejudice to the school.
The 15 spare places is a red herring in all this. The school cannot just magic up an extra 15 places when they want to. Year 2 has a PAN of 60 and therefore the school has by law to admit to 60 but when year 2 moves to year 3 and year 1 moves to year 2, it does not mean that year 2 has more places, the PAN stays with the cohort as it moves through the school. The PAN next year in year 2 will be 45 as it is now with the cohort in year 1.
I am not sure how they can make a case based on floor areas if they have 6 classes which are of a size for 30 pupils or have been in the past. What exactly are they saying?
The initial rejection from the school to my mind was in correct. They somehow believe that it is an infant class size appeal whereas the data says it should not be. The decision to not admit should have been based on the school having exceeded the PAN and other factors, that is a normal prejudice case.
There is something very wrong here in somebodies understanding of Infant Class Size legislation or in our knowledge of the school and probably the best think is to wait until the formal papers come out and we can see exactly what the case is being based on.