You could take a look at the link below:http://www.cambridgeesol.org/exams/exam ... index.html
It should take you to the UCLES FAQ page where your question is answered in full.
I've just spent some time on the UCLES website and it wasn't easy to find the answer to your question. It's hidden away!
If the link doesn't work, go to UCLES EFL exams home page; click on exams / FAQs (hidden in the bottom right) / General Main Suite.
Hope this helps,