Okay to Underachieve with the word limit?

I was actually finishing up an essay for one of my universities that asked about why I would like to attend one of their specific schools of study. The essay’s word limit was 500, but my essay hit only 320 words. I wanted to ask if the word limit is there to suggest the approximate amount of words college applicant reviewers want from an essay or if it is only there to keep a cap on the essay’s size. If i should write more, could anyone suggest some topics I could discuss or specific points in my essay that colleges would like if I elaborated upon them?

Thanks for the help!

I think you should try for 450. I mean this is the place to sell your passion for their school. Too short looks like you’re not that jazzed.