My brother-n-law was cooking with the charcoal grill the other weekend. He pilled the charcoal on the side with the vent opening instead of the other side. This allowed 3 small hot coals to fall out fo the grill and put small burn marks on my precious roof. They're each about the size of a quarter and only marked the top. I don't think it burned down to the wood, but there was no white left when I scrubbed at it. I need to touch this up to ensure it's protected. What do I need to do to fix this?