I'm just back from the PRNC and if I am remembering correctly it is only pay as you dine once you complete basic training. During the initial 10weeks your meals will be automatically deducted from your monthly salary, as well as your accommodation.
I've just done the 10 week App Seaman course at Raleigh and nothing was deducted from my wages - neither food nor accommodation.
It was pay as you dine but only if you go above the standard meal or choose more than 3 proteins at brekkie.
Your name is in a list at the till along with the rest of the course your with. You sign for each standard meal whilst the food police check you've not had anything above the standard menu.
If you do decide to upgrade to the chefs special (hot chips instead of lukewarm!) as long as you get your receipt you can claim it back on a 305.
I then went to Collingwood for 2 weeks and there I paid for all my meals I kept my receipts and claimed them back on a 305.