Hi.
Come of the track one stride before you hit R and you should be aiming to be just before the Letter I that runs down the middle of the arena. Then back on the track again directly at R.
I tried do draw a little diagram but it would not come out ok on the screen. :-(
No directly at R you should be of the out side track and starting your circle.
Then back on the outside track directly at R.
Make sure your horse is nice and straight befor you get to R and then bring your inside leg on and a little inside rein to bring the horses head into the circle, you should be able to see the inside eye a little more. That way you will be able to creat a nice balnced 15m circle.
Good luck!!!