Ann: Afterpay Share Purchase Plan, page-68

As per my understanding, SPP for 30mil is final and doesn't need any approval etc.

Also, 15k ceiling for an individual is enforced by the ASX, not APT. As per the rules, the maximum amount an individual investor can use for SPP for a particular stock is 15k in any 12 months period. In simple terms, if you bought 10k worth of shares in their last SPP less than 12 months ago, you are entitled to apply for only 5k more.
In this case, as their last SPP was more than 12 months ago, eligible holders are entitled to apply for full 15k.