To fix the issue, you can adjust the properties on the Duplicate Status VF Page so that it is set tall enough to display the two buttons while they are stacked vertically on your smaller screen device.
To adjust the Duplicate Status VF Page Properties:
- Click Contacts in the top menu
- Click the name of any Contact Record
- In the upper right corner of the record click Edit Layout
- Find the Duplicate Status Field and hover over it to display the properties icon, then click the properties icon
- In the properties for the Duplicate Status Visual Force Page set the property for Height (in pixels) to 65 pixels
- Click Save