You can’t pick sustainability and then state that it doesn’t matter as this wouldn’t make it a relevant implication.
Describing Relevant Implications (Achievement)
This involves defining the chosen implication generally.
For example future proofing is about ensuring that the finished product / outcome will be suitable for use after it has been completed and will remain usable for the agreed lifetime of the outcome.
Your goal here is to demonstrate that you know what future proofing is not how to adress it.
Explaining/Addressing how a design/outcome meets relevant implications (Merit)
to do this you need to consider the positive and negative impacts of your outcome on the implication.
Then write a summary weighing up these points and demonstrating how you will or have minimised and negative aspects of the implication and included or enhanced any positive aspects of the implication.
For example with future proofing you could minimise a negative impact of a print media outcome by laminating the posters that are displayed on a wall as this would increase their longevity. A consequence of this is that they are less environmentally friendly.