Remove the paddings from RelativeLayout
:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.debitdistance.WifiChartsRealTime$PlaceholderFragment" >
...
</RelativeLayout>
These are the reason of not 100% filling the screen.