As a recent letter in the Chad says, these “signals” at road islands are confusing and extremely annoying for other drivers.
The general rule, on approach to a traffic island, is if you are given the option of lanes and intend to turn right, then select that lane.
Another tip to help you is that if your intended turn is past 12 o’clock, then always indicate as you approach as well as selecting the correct lane.
Leave your indicator on until you’ve passed the turn off, before you then change to a left hand indicator in order to show your intended route to anyone – pedestrians as well – that you are leaving the roundabout.
This is called “a breakaway signal” for obvious reasons.
Get into the habit of doing it, even if there is no one around. It saves other road users becoming frustrated and angry at you.
Ex-police traffic officer