That’s because in roundabouts you have an extra turn to the left and then right (or I suppose right and then left in America?) so you’re adding 90 degrees twice to your 180 making it a 360. The math adds up at least
(In the US) You would make a 90° turn to the right to enter the roundabout, a 360° turn to the left (putting you back in the same spot as when you entered the roundabout), then another 90° turn to the right to exit.
That’s because in roundabouts you have an extra turn to the left and then right (or I suppose right and then left in America?) so you’re adding 90 degrees twice to your 180 making it a 360. The math adds up at least
*subtracting 90° twice
(In the US) You would make a 90° turn to the right to enter the roundabout, a 360° turn to the left (putting you back in the same spot as when you entered the roundabout), then another 90° turn to the right to exit.