RTH means “Return To Home”.
ANAFI Ai features a Smart RTH capability: considering its altitude and its distance from its take-off point, the drone computes in real time the power it needs to return home – or to the pilot, or to a custom location (refer to the “PREFERENCES / Safety / Advanced RTH settings” of this guide for additional details on this feature). When short on battery power, FreeFlight 7 alerts you that it will enter automatic RTH mode.
If you feel confident you can bring ANAFI Ai back to its take-off point or if you wish to land it at a different location, you can cancel the auto-RTH directly from the alert pop-up.