This graph shows organic search engine result visits for the period from Bing. Please note that if you are running a PPC advertising campaign with Bing,then you will need to ensure your advert's URLs are set up properly with URL tracking so that your PPC paid click-thrus are not reported as organic non-paid click-thrus.
For further information on how to set up PPC tracking correctly with Bing please visit our blog on the subject.