Col, spoke to my mate and he clarified things.
The overflow is for ADFA. There are way more ADFA applicants than there are spots. So a competitive process. If an ADFA bod missed out and they still wanted to get into ADFA they had to go through the whole process again at recruiting. To alleviate this, PSF has allocated a couple of courses for ADFA at the start of the year for the next year. This does not mean it’s still not competitive as a lot still won’t be offered a spot.