Hi Dory,
I checked some of your segments and campaigns and this is what I found:
When you define a segment to match visitors from Healthcare organizations for example, this segment will match these visitors as they land on your website, regardless of the page they view.
The 'Campaign Target URL' you set in the Campaign editor defines which specific page or pages the campaign will be displayed on.
Looking in the 3 campaigns from your screenshot ('Healthcare In Zone', 'Finance In Zone' and 'Media In Zone'), they all have your home page (www.emarketer.com) defined as the target URL.
Therefore, the number of impressions you see on the Campaigns page indicates the number of visitors that matched the campaign’s target segment and actually were on the home page and saw the campaign.
Let me know if you have any further questions,
Yanir.