split_configuration_placeholder.xml

<?xml version="1.0" encoding="utf-8"?>
<resources xmlns:window="http://schemas.android.com/apk/res-auto">
    <!-- Other rules -->
    <SplitPlaceholderRule
        window:placeholderActivityName=".details.DetailsPlaceholderActivity"
        window:splitRatio="0.4">
        <ActivityFilter window:activityName=".list.ListActivity" />
    </SplitPlaceholderRule>
</resources>