What they need from you here is something that can let them know about your two abilities. This can be a comment or a novel, and there are no fixed restrictions.
As far as copywriting planning in the game industry is concerned, you can choose to bring two works. One is short stories or poems, essays, etc. But show your writing skills, not just pile up gorgeous words. Because as a planner, more requirements are clear and accurate written expression. You need to grasp this aspect yourself. The other is your analysis and comment on the most popular game on the market. Generally speaking, there is no standard answer to this kind of analysis and comment, but you need to show that you are more comprehensive and unique in looking at a product than others.
Finally, the reason why the interview is an interview is that more than 80% of the comments come from face-to-face chat and investigation. So, don't focus too much on your work, just let nature take its course and come up with the works that can best show you. The rest is to behave well in front of the interviewer.