I've only tried this a couple of times, but I think this is what I did.
1. Select the dronie option
2. A distance slider appears along the bottom edge of screen, set to a default of 40m. Change this to your required distance.
3. Select point of interest and off you go.
Looks like between step [1] and [2], I need to tap the screen in order to see the slider.
But thanks for steps, I finally was able to adjust the distance.