Nothing is wrong here.
For example let us consider the returned string is
Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
Then the explanation is
ChromeChrome 41.0.2228.0
Mozilla ==>
MozillaProductSlice. Claims to be a Mozilla based user agent, which is only true for Gecko browsers like Firefox and Netscape. For all other user agents it means 'Mozilla-compatible'. In modern browsers, this is only used for historical reasons. It has no real meaning anymore
5.0 ==> Mozilla version
Windows NT 6.1 ==> Operating System Windows 7
AppleWebKit ==> The Web Kit provides a set of core classes to display web content in windows
537.36 ==> Web Kit build
KHTML ==> Open Source HTML layout engine developed by the KDE project
like Gecko ==> like Gecko...
Chrome Name ==> Chrome
41.0.2228.0 ==> Chrome version
Safari ==> Based on Safari
537.36 ==> Safari build
Description: Free open-source web browser developed by Google.
Chromium is the name of the open source project behind Google Chrome, released under the BSD license.
You can find more information in below link
http://www.useragentstring.com/pages/Chrome/
click on each link on the page to get more info