Basically, the application task is a long-winded take-home assignment. You will get a topic which is an extension of what you have currently learnt, and the questions in the SAC will guide you through an application of this topic (you will of course have to make the conclusions yourself). My SAC consisted of 1 question which had 10 parts.
Since it is a take home task and since it contributes so much to your SAC score, I would recommend you spend as much time as you can on it. Before you start, do a draft of what you're going to write. Flesh out your answers (I lost a mark for not doing this) as much as you can (you've got plenty of time), and check over your work afterwards. Good luck!