Does anyone know what the 'A level with additional AS (9 units)' means On the UCAS form? Thank you!
You've almost certainly not done it, as far as I'm aware it's not really a mainstream qualification. If you've done an AS, you need to choose Advanced Subsidiary (i.e. 3 units). If you've done an A2, you need to choose Advanced Level (i.e. 6 units). That qualification would be some kind of extended A level with 9 units but I've never heard of it.
It's halfway between an A level and a double A level.
It isn't common. If you haven't been told that this is what you're taking rather than standard AS and A levels then do not say that you're taking this qualification on your application.