ok, everyone's pretty much said it. i did music1 last year and my composition portfolio had hardly anything in it.... all my drafts, some notes on encore, some pieces of music that i listened to and inspired me, some ideas for a melody, a review on an excursion to the con where we workshopped with a composer, all my notes on why i didn't like this, why id idn't like that etc etc....
talk to your teacher about it, my teacher gave us lots of help and showed us diaries from past years etc. besides, the board only request to see your diary IF they find something dodgy with your composition.