"Setting new Return-To-Home altitude to nnn (nnn)"

This is simply letting you know that the Return-to-Home altitude has been set.

Some drones will automatically Return-to-Home if the signal between the drone and RC is lost. This is the altitude at which the drone will fly back.

When setting the RTH altitude, it's recommended that you check your surroundings for obstructions as well as current wind conditions at varying altitudes.

If not necessary, we don't advise setting the RTH at the maximum allowable altitude, as winds are typically stronger when higher up.