@android:targetSdkVersion '17' is less than $(TargetFrameworkVersion)

...\Droid\Properties\AndroidManifest.xml: Warning XA4211: AndroidManifest.xml //uses-sdk/@android:targetSdkVersion '17' is less than $(TargetFrameworkVersion) ''. Using API-22 for ACW compilation. (XA4211)

I cannot start debugging my app. After I changed an icon I noted the warning above.

So what is the target framework version and where to I set it?