In regards to number of interviews, the number is roughly 400-500 however sources close have told me that this year has had the most number of applicants so competition is high this time around (not to say other years weren't).
As for awards to put into your folio, try and not to "scrape from the bottom of the barrel" (E.g Primary school awards/trophies unless you're still doing the activity in the present year) which I know may seem hard to do but I'd say 3-5 years is a good range. Take photos of medals and trophies and copy it onto a word document with a title underneath should do the trick (also mention year and what the award is if it's hard to tell at first glance).
In terms with the interview, try not to have rehearsed answers since if you can't answer a question "naturally" (I.E Not in the same tone as previous answers) then it'll look bad (and they've been doing this for a number of years so they've learnt what to look out for).
Good luck for those tomorrow and enjoy the scenery at JMSS (and don't worry about JMSS students walking past you and all too since most will be reminiscing about their interview experience xD)