Irritating error messages after setting up Android Tools

After specifying the Android tools paths in the Options dialog, and after pressing OK, I get these error messages in the General Messages tab:

The system cannot find the path specified.
Project ERROR: You need to set the ANDROID_NDK_ROOT environment variable to point to your Android NDK.
Could not read qmake configuration file C:/Qt/Qt5.3.0/5.3/android_armv7/mkspecs/android-g++/qmake.conf.

However, everything works: Building, deploying, etc. So, what do these error messages mean, and where do they come from?