Activities Essay? How do I write one?

What is the word limit for the activities essay? I have heard some people say it is 150 while others tell me I can write 250-400 words. I am applying to the UCs and also through the Common App. Are the word counts different?
How should I write my activities essay? Is it better to have a concrete story or example or just to talk about my experience? I have done marching band but I was never a leader or anything. Should I still write about marching band?
One more question! For the UC application, is it better for one of the main essays to be long and the other short or for both to be around 500 words? Thanks!

I know this is going to seem like a really bad answer, but you should write about whatever is most important to you. Either a single narrative story or a series of “examples” is fine. The length of the individual UC essays should be dependent on what you’re writing about. If they end up being both around 500 words, that’s fine. If one is 300 and the other is 700, that’s also fine.