Question about Scantrons?

Hi.

I took AP Comp Sci today and I nearly ran out of time at the end. I had filled in my answers somewhat lightly because I was planning on going back and reviewing them.

My question is: how do the scantrons work - and will my lightly-ish filled-in bubbled register in the machine? Or will I end up having to request a hand-scored version?

If anyone has experience with this I appreciate your help!