Kumite rules are a little bit confusing, specially if you are not familiar to Karate at all. Many people have argued over the years that this was one of the main reasons that it was so hard for Karate to be considered an Olympic sport; it was simply not that attractive.
As an athlete myself, I`d have to say that even for us sometimes was complicated, because the rules changed so much during the years.
In case case, regarding the scoring system, this is a nice simple video that the WKF made.
Share it with your parents! They will appreciate it!