If you paid on motorsportreg.com, it's a delayed transaction so you won't be charged until after the event. You're not required to pre-pay but if you do, you can get a refund unless you've gone through tech before the 1st day. On the 2nd day (say you break on the 1st day), you can get a refund as long as you haven't been on track yet. The 3rd day (doesn't apply to you since there are no Novice sessions on Sunday) is free for everyone so refunds don't apply.