Don't worry; Google aren't going to care if just one person comes along and that person is interested in two of the ads that they see (hence you get a 200% click-through rate). Google know that a few people and a few clicks leads to crazy percentages.
One of my sites often gets a 100% click-through rate on a day, because one person comes along (in that month!) and leaves straight away through one of the ads.
Google will care if 486 people visit your site and you're still getting a 200% click-through rate!