In the Visitor - Settings view. the Plugins panel gave is showing these numbers for (in the attached screenshot): Please note the 102% in the first line. It might be a small issue related to visitors using ie browser. But it could be a general problem with calculating percentages on the entire webapp. It is worth it to take a look at the math.
I am using Piwik 2.11.2. And the project was noticed with "All Visitors" segment but also with other segments.