Subscription fees work a little differently to All Or Nothing campaigns, so here's the go;
Platform fees won't be charged until your profile has $100 or more in subscriptions per month. Once you start earning AUD$100 or more a month, you'll be charge 5% of subscriptions/month.
Merchant fees are Stripe's fees (& are slightly more confusing). These are AUD$2/month + 0.25% of account volume, then 25c per payout. Check out these fees in more detail here - https://stripe.com/au/connect/pricing