Seems like an okay deal for the 35 day prepaid $40, giving 12.5GB per 35 days. Must opt in with a text message saying '35' to 1263. I haven't got my father to try the text message out yet so can't confirm with or without quote marks. My guess is, either will work.
Start it any time before 31/1/18 and it will last up 10 consecutive months depending when you activate. I believe it will start on next recharge.
From the promo page.
Check out our incredible Prepaid deal that just keeps on giving.
To celebrate the festive season, we’re giving you the chance to score up to 35GB bonus data over ten $40+ Data or Talk Combo recharges. Opt in by texting ‘35’ to 1263 before 31 January 2018, then recharge on a $40 and above Combo to get 3.5GB bonus data for up to 10 recharges until 15 November 2018. All to use in Oz. T&C apply.
Can confirm the bonus is on your next recharge.
And no quotes required, i.e. just TEXT 35
Works on both $40 and $50 recharges