Abbreviations On The Common App?

<p>This might seem like a dumb question, but I'm just making sure because I want everything in my application to be perfect... :)</p>

<p>On the Common App, is it ok to use abbreviations for things?
Like specifically, on the Activities section, in the box where one is to "List the specific activity here, and provide details if needed."
I'm trying to explain what my role in each activity is, to more accurately paint a picture of what I do. Would it be ok to use abbreviations such as "Sr" for "Senior" and "Jrs" for "Juniors" and the like, to make it easier to fit things in that tiny box? Or would the AdComs "not know" what I am talking about?
I know not to go crazy and use obscure abbreviations that outsiders don't know, but I think pretty much everyone knows what Jr. means...</p>

<p>Example:
"Yearbook: Oversaw entire production; designed Sr Boxes, Jrs, Student Life, and Sports/Clubs pages"</p>