The Administrative Guide to Using Submit for Assessment (p2) (for exams officers), it states all pages should be no larger than A3. The subject-specific Guidance on the Administration and online submission of Art & Design, it says A2. Can you Clarify?

We have suggested A3 as a reference in the guidance material to try and help teachers and students keep within the 25 GB file size for upload, as specified in the Submit for Assessment Administrative Guide.

If you find that the A2 size would work better for you and your students, then you are able to digitally compose and layout the work using the A2 dimensions. However, you must ensure that the total file size for each candidate for each component does not exceed the 25 GB limit.